Rozprawy doktorskie na temat „Grapes Growth”

Thesis (MSc)--Stellenbosch University, 2002.
ENGLISH ABSTRACT: The cultivation of table grapes in the warmer areas of South Africa, indeed worldwide, is complicated by rest breaking problems in spring due to delayed budbreak. In order to overcome these problems rest breaking agents, mainly hydrogen cyanamide, are applied. However, instead of alleviating the problem, additional problems such as uneven budbreak and reduced production are often induced. This study was initiated to further understand the physiological processes occurring during budbreak and how the application of hydrogen cyanamide influences these processes. The following aspects were investigated in this study: a. The effect of hydrogen cyanamide on tissue cytokinin (specifically zeatin riboside) levels of Sultanina table grape vines after application at different times before natural budbreak was studied over two seasons. In 1997, hydrogen cyanamide was applied at three weeks before induced budbreak and in 1998 at six weeks before induced budbreak. One year-old canes were sampled weekly after hydrogen cyanamide application, divided into distal and proximal sections, then further divided into buds, bark and wood tissues and the zeatin riboside (ZR) levels determined. A relatively high amount of chilling coupled to late hydrogen cyanamide application in 1997 led to a large effect on ZR release, but did not lead to significant shifting of the budbreak pattern. Zeatin riboside peaks were observed in buds, internode wood and bark of treated vines compared to control vines. The peaks were higher in distal portions compared to proximal portions in all tissues. The relatively lower chilling and earlier application of hydrogen cyanamide in 1998 had a larger effect on the budbreak pattern while the bud ZR peak was shifted earlier. The distal portion bud ZR . peak was again higher than the proximal portion bud ZR peak. In 1997, as sampling was not initiated early enough, bud ZR peaks were only observed after budbreak, while in 1998 bud ZR peaks were observed before and after budbreak. The effect of these ZR increases on the development of inflorescence primordia, subsequent bunch development and ultimately production, are discussed. b. Free xylem sap was sampled at cane and spur pruned lengths from unpruned canes of Sultanina from budswell until after budbreak in 1999 and from three table grape cultivars, i.e Sultanina, Alphonse Lavalleé and Sunred Seedless, in 2001 and ZR levels determined. The ZR levels in the buds of these three table grape cultivars, pruned to different cane lengths were also determined. One year old canes of these cultivars, were each pruned to long canes (14 buds) and short spurs (2 buds). The ZR content in buds of these canes at distal and proximal positions were determined weekly from budswell until after budbreak in 1999. Xylary ZR peaks occurred before 50% budbreak. Spur xylary ZR levels of all three cultivars followed a similar pattern, although at lower ZR levels than that of the canes. This is similar to previous studies on xylary ZR levels of apple shoots. The high levels of free ZR found in xylem sap at the distal portions of canes support the hypothesis of a cumulative ZR build-up effect as cane length increases. Spur pruning resulted in earlier budbreak and a higher final budbreak than cane pruning. The proximal portions of shoots, whether spur pruned or the proximal portions of canes, showed elevated ZR levels in all cultivars. This difference in ZR levels in bud tissue of different portions of the cane would suggest a difference in ZR consumption or turnover. The results of this study have important management implications for the cultivation of vines in warmer areas in which hydrogen cyanamide is used to alleviate budbreak problems.
AFRIKAANSE OPSOMMING: Die verbouing van tafeldruiwe in die warmer gebiede van Suid-Afrika, soos straks wêreldwyd, word bemoeilik deur rusbreekprobleme in die lente weens vertraagde bot. Rusbreekmiddels, meestal waterstofsiaanamied, word gevolglik toegedien om hierdie probleme te probeer oorkom. In plaas van opheffing van die probleem, veroorsaak hierdie toedienings somtyds addisionele probleme soos ongelyke bot en verlaagde produksie. Hierdie studie is aangepak om die fisiologiese prosesse wat tydens bot plaasvind, beter te verstaan, asook hoe die toediening van waterstofsiaanamied hierdie prosesse beïnvloed. Die volgende is in hierdie studie ondersoek: a. Die invloed van waterstofsiaanamied op lootweefsel sitokinien (naamlik zeatin ribosied, ZR) vlakke van 'n Sultanina tafeldruif wingerd is oor twee seisoene ondersoek na toediening op verskillende tye voor bot. Waterstofsiaanamied is in 1997 drie weke en in 1998 ses weke voor geïnduseerde bot toegedien. Een jaar oue lote is weekliks gemonster na waterstofsiaanamied toediening, verdeel in apikale en basale gedeeltes en verder verdeel in ogies, bas en houtweefsel en die ZR vlakke bepaal. Relatief hoër vlakke koue, gekoppel met later watersiaanamied toediening het in 1997 tot 'n groot effek op ZR vlakke gelei, maar het nie die botpatroon wesentlik verskuif nie. Zeatin ribosied pieke is waargeneem in ogies, internode hout en bas van behandelde wingerd in vergelyking met kontrole wingerd. Die pieke was hoër in apikale gedeeltes in vergelyking met basale gedeeltes in alle weefsels. Die relatief laer koue en vroeër toediening van waterstofsiaanamied in 1998 het 'n groter effek op die botpatroon gehad, terwyl die ogie ZR piek vroeër geskuif is. Die apikale gedeelte se ogie ZR piek was weereens hoër as die basale gedeelte se ogie ZR piek. Monstering was nie vroeg genoeg begin in 1997 nie, aangesien ogie ZR pieke slegs na bot waargeneem is, terwylogie ZR pieke in 1998 voor en na bot waargeneem is. Die effek van hierdie verhoging in ZR vlakke op die ontwikkeling van blom primordia, daaropvolgende tros ontwikkeling en uiteindelik produksie, is bespreek. b. Vry xileemsap is gemonster van langdraer en kortdraer gedeeltes van ongesnoeide lote van Sultanina vanaf ogieswel tot na bot in 1999 en vanaf drie tafeldruif kultivars, naamlik Sultanina, Alphonse lavalleé en Sunred Seedless, in 2001 en die ZR vlakke bepaal. Die ZR vlakke van ogies van hierdie drie kultivars, gesnoei tot verskillende lootlengtes is ook bepaal. Eenjarige lote van hierdie kultivars is gesnoei tot langdraers (14 ogies) en kortdraers (2 ogies). Die ZR vlakke in ogies geleë op apikale en basale gedeeltes van hierdie lote is weekliks in 1999 bepaal vanaf ogieswel tot na bot Xileemsap ZR pieke is waargeneem voor 50% bot. Kortdraer xileemsap ZR vlakke het 'n soortgelyke patroon as die langdraers gevolg vir al drie kultivars, alhoewel teen laer ZR vlakke as die langdraers. Hierdie waarneming is soortgelyk aan vorige studies op xileemsap ZR vlakke van appel lote. Die hoë ZR vlakke gevind in die xileemsap van die apikale gedeeltes van lote ondersteun die hipotese van 'n kumulatiewe opbou van ZR soos die lengte van die loot toeneem. Die snoei van lote as kortdraers het gelei tot vroeër bot en 'n hoër finale bot persentasie as die snoei van langdraers. Die basale gedeeltes van lote het verhoogde ZR vlakke in al drie kultivars getoon, onafhanklik van die feit dat dit vanaf die kortdraer of die basale gedeelte van 'n langdraer was. Hierdie verskil in ZR vlakke in ogie weefsel van verskillende gedeeltes van die loot impliseer 'n verskil in ZR verbruik of omset. The resultate van hierdie studie het belangrike bestuursimplikasies vir die verbouing van wingerd in warmer gebiede, waar waterstofsiaanamied gebruik word om botprobleme te oorkom.

Copies of author's previously published articles inserted. Bibliography: leaves 143-167. Temperature may affect fruit-set in grapevines through its effect on the development of the flowers up to flower opening and on pollination, be it on the germination of the pollen and the growth of the pollen tube, or on the post-fertilisation growth of the ovule.

Thesis (MScAgric)--Stellenbosch University, 2004.
ENGLISH ABSTRACT: The effect of shoot heterogeneity on vegetative and reproductive growth parameters, vine physiology and grape composition was investigated in a ShirazlRichter 99 vineyard. Comparisons between underdeveloped (typically shorter and less ripened at véraison) and normally developed shoots in both shaded (non-manipulated) and well-exposed (manipulated) canopies were made. Compared to underdeveloped shoots, normal shoots had a larger total leaf area, due to the higher occurrence of secondary shoots as well as larger leaves on primary and secondary shoots. Since the photosynthetic activity of the leaves from normal shoots was higher than those from underdeveloped shoots, higher levels of carbohydrates were produced and stored in the former. Starch was more evenly distributed over the length of the whole shoot in normally developed shoots compared to underdeveloped shoots. Normally developed shoots were longer and thicker in diameter than underdeveloped shoots. The larger clusters of the normally developed shoots are evidence of their more favourable total leaf area per gram berry mass. Berries from the normally developed shoots were smaller at five weeks after véraison than those from underdeveloped shoots, displaying a higher skin to pulp ratio and therefore higher anthocyanin and total phenolic extraction potential for winemaking. The smaller clusters and fewer berries per cluster found for the underdeveloped shoots indicate an imbalance between vegetative and reproductive growth initiated during the vegetative growth phase and continued during the ripening period. The peculiar absence of statistically significant differences in grape composition between normally and underdeveloped shoots indicates that assimilates needed for berry ripening of the latter originated in organs other than the leaves [e.g. from adjacent normal shoots and the rest of the permanent structure of the vine (cordon, trunk, roots)]. The larger differences in berry size that occurred between shoot types in the shaded compared to the well-exposed canopies may be evidence for this. The photosynthetic activity of shoots was lower in shaded than in exposed canopies. The total carbohydrate production of the normal shoots in shaded canopies seemed insufficient to supply in the ripening needs of the shoot itself, their own clusters as well as the ripening of stem tissue and clusters of the underdeveloped shoots in the canopy. This is illustrated by the lower levels of starch that accumulated in the normal shoots from shaded compared to that of exposed canopies. Vine shoot heterogeneity clearly leads to visible and physiological imbalances that would impact negatively on grape and wine quality as well as production costs and should therefore be avoided on any terroir.
AFRIKAANSE OPSOMMING: In hierdie studie is die effek van heterogene lootontwikkeling in die lower van 'n ShirazlRichter 99 wingerd ondersoek. Vergelykings is getref tussen normale en onderontwikkelde lote in beskadude en blootgestelde lowers ten opsigte van hul vegetatiewe en reproduktiewe groeieienskappe, fisiologiese aktiwiteit en druifsamestelling en -gehalte. 'n Groter totale blaaroppervlak het by die normaalontwikkelde lote voorgekom as gevolg van die groter aantal sekondêre lote en groter primêre en sekondêre blare. Aangesien die blare van die normaal ontwikkelde lote fotosinteties meer aktief was as dié van onderontwikkelde lote, het die eersgenoemde lote groter hoeveelhede koolhidrate geproduseer en gestoor. Styselopberging het meer eweredig oor die lengte van die normale lote plaasgevind. Laasgenoemde lote was ook heelwat langer en dikker in deursnee as die onderontwikkelde lote. Die gunstiger totale blaaroppervlak per korrelmassa verhouding van die normale lote is duidelik weerspieêl in die groter trosse, terwyl die kleiner korrels (en dus die groter dop:pulp verhouding) op 'n groter potensiaal vir kleur- en fenolekstraksie tydens die wynbereidingsproses dui. Die kleiner trosse en kleiner aantal korrels per tros wat by die onderontwikkelde lote gevind is, dui op 'n wanbalans tussen die vegetatiewe en reproduktiewe groei van die loot wat tydens die vegetatiewe groeifase van die wingerdstok geïnisieer is en tydens die rypwordingsperiode voortgesit is. Die vreemde afwesigheid van enige statisties betekenisvolle verskille in druifsamestelling tussen die normale en onderontwikkelde lote dui daarop dat die verbindings wat vir die rypmaking van trosse op onderontwikkelde lote aangewend is, waarskynlik van ander wingerdorgane (bv. naasliggende lote, kordonarms, stam, wortels) as die spesifieke loot se blare afkomstig was. Die waarneming dat die korrelgroottes van normale en onderontwikkelde lote meer van mekaar verskil het in die beskadude as blootgestelde lowers, kan moontlik as bewys hiervoor dien. Die fotosintetiese aktiwiteit van beide loottipes was laer in die skaduryke lowers. Die koolhidrate wat deur normaalontwikkelde lote in skadu-Iowers geproduseer is, was oênskynlik onvoldoende vir die rypmaking van die loot self, die spesifieke loot se trosse, asook die trosse en lootweefsel van naasliggende onderontwikkelde lote. Hierdie bewerings word gerugsteun deur die laer vlakke van styselakkumulasie wat by die normale lote in beskadude lowers gevind is. Aangesien heterogene lootontwikkeling en -groei duidelike sigbare en fisiologiese wanbalanse in die wingerdstok tot gevolg het wat negatief op druifsamestelling, wyngehalte en produksiekoste inwerk, behoort dit in kommersiêle wingerde vermy te word.

"Department of Horticulture, Viticulture and Oenology, Faculty of Agriculture and Natural Resource Sciences, The University of Adelaide, Waite Campus, Glen Osmond S.A." Bibliography: leaves 136-149 This investigated focussed on selected aspects of berry development and ripening that were subject to variation. Shiraz and Chardonnay were chosen as experimental varieties because these cultivars presented a large range of variability in the field. The extent of the variation within each of the recorded berry parameters was assessed using the coefficient of variation (CV), a unitless measure of sample variability relative to the sample mean, ideally suited to comparative studies.

The effect of hydrogen cyanamide (H₂CN₂) on budbreak and fruit maturity of 2-year old 'Flame Seedless' table grapes was investigated in a low desert climate in central Arizona. Dormant sprays of H₂CN₂ applied at 2.5 and 5.0% (v/v) concentrations hastened budbreak by at least 16 days with subsequent advancement of fruit maturity by 5 to 10 days. A 5.0% (v/v) dormant application of H₂CN₂ to whole vine, buds only or pruning cuts only advanced budbreak by at least 16 days and advanced fruit maturity by 1 to 5 days, regardless of application site. A more uniform budbreak was observed on H₂CN₂ treated vines, regardless of concentration or site of application when compared to control vines.

Thesis (MScAgric)--Stellenbosch University, 2003.
ENGLISH ABSTRACT: In the past it was very difficult to visualise the extent and distribution of variability in growth vigour within vineyards. The advancement of remote sensing technology has changed this however, establishing new methods to assess and manage variability. Even though the causes and effects of within-vineyard variability in growth vigour are complex, new technologies offer better ways of monitoring, researching and managing these factors. In addition to the possible benefits of aerial or satellite remote sensing, new methods of mapping soil spatial variability as well as advances in georeferencing technologies supply precision tools to both researchers and producers. The scientific advancement of the technology, however, is currently the most important aspect needed. This is crucial to answer and explore fundamental questions regarding the use of the technology and the interpretation of results within the framework of the plant's observed reaction. Only then can the possible applications in vineyard management be optimised to address the management problems of extensive within-vineyard variation in growth vigour. The choice will always be to use the technology to manage the observed variability in order to limit the negative impacts of a heterogeneous harvest, or to identify the variability and its causes for the implementation of management practices aimed at a more homogenous vineyard and harvest. Whatever the case, extensive research is needed to provide tight correlations between information gathered with new technologies to assess variability and plant status, such as multi- and hyperspectral analysis, and ground-truthed results in the vineyard. Only then will it become evident which methods and analyses would be useful in the drive towards in-depth analysis and management of vineyards within the concept of precision viticulture and its derived advantages. With this in mind, the aim of this study was to establish an experimental model to use remote sensing technologies to identify and classify within vineyard variability with a subsequent analysis of the causes of variability and the effects on the plants. The targeted experimental model was a vineyard with highly heterogeneous above-ground growth. An aerial photograph of the vineyard was studied and manipulated to yield image pixel values used to quantify the degree of variability for different plots, which were chosen according to different plot layouts. Soil conditions were assessed on both a global and plot level, with extremely high pH and low resistance values in the soil in combination with erratic soil preparation practices found to be the main cause of variability. Soil physicochemical condition was also assessed during a soil profile pit study. Significant differences were found between several soil-related parameters measured for the higher and lower vigour levels and a strong correlation was also found between the resistance of a saturated soil paste and the image pixel values. Vegetative measurements also yielded highly significant differences between the vigour levels and confirmed the suitability of the vineyard to study within-vineyard variability. Some of these measurements were also strongly correlated with soil conditions as well as image pixel values. Trunk circumference proved to be an excellent measure for the level of variability, being linked strongly to canopy characteristics, soil conditions as well as the image pixel values. Leaf water potential measurements also yielded significant differences between the vigour levels. Harvest data and wine analyses showed the effect that vigour differences can have on grape composition and wine quality, even though the differences found here were much less than expected. Even though no clear preference was shown between the wines made from the different vigour levels, the lower vigour wine was considered fruitier. The overall quality of both experimental wines was however very high, considering that experimental winemaking techniques has been used. Hyperspectral measurements also confirmed differences between the vigour levels through a narrow-band NOVI (normalised difference vegetation index). It was also possible to show differences in certain biochemical compounds between the vigour levels on both a leaf and canopy level. Wavelength regions corresponding to carotenoid, chlorophyll a and chlorophyll b showed different spectral reactions in the leaves of more stressed (lower vigour) canopies, indicating possibilities for further studies. This study and its results is the first of its kind in the South African wine industry and paves the way for more focussed and in-depth analyses of the use of specifically multiand hyperspectral data to accurately assess within-vineyard vigour variability and the management thereof to yield optimum quality grapes for a specific wine target. Moreover, the approach adopted in this study is also echoed in other international research programs in prominent wine countries. The availability of scientific research regarding the optimal use and limitations of these technologies has the potential to revolutionise production management practices in the next few years in the viticultural industry.
AFRIKAANSE OPSOMMING: In die verlede was dit baie moeilik om die omvang en verspreiding van groeikragvariasie binne 'n wingerd te visualiseer. Die vordering gemaak op die gebied van afstandswaarneming-tegnologie het egter nuwe metodes beskikbaar gestel waardeur hierdie variasie in wingerde gemonitor en bestuur kan word. Selfs al is die oorsake en invloede van binne-wingerd-groeikragvariasie kompleks, verskaf nuwe tegnologieë verbeterde metodes om hierdie variasie te monitor, te bestuur en na te vors. Saam met die moontlike voordele wat lugfoto's en satelliet-afstandswaarneming teweegbring, verskaf nuwe metodes om ruimtelike variasie in grondfaktore te karteer, asook vordering in geoverwysingstegnologie, presisiehulpmiddels aan produsente én navorsers. Die wetenskaplike vordering van dié tegnologie is tans van groot belang. Die belang daarvan is om fundamentele vrae te ondersoek en te beantwoord rakende die gebruik van die tegnologie en die interpretasie van resultate binne die raamwerk van die waargeneemde reaksie in die plant. Dit sal die weg baan vir optimale toepassing van die tegnologie in wingerdbestuur om sodoende die bestuursprobleme wat deur binne-wingerdgroeikragvariasie teweeggebring word, aan te spreek. Die voorkeurkeuse is om dié tegnologie aan te wend om hierdie variasie te bestuur sodat die negatiewe impak van In heterogene oes teengewerk kan word, of om die variasie te identifiseer vir die implementering van bestuurspraktyke gemik op die skep van 'n meer homogene wingerd en oes. Dit is noodsaaklik dat uitgebreide navorsing gedoen word om noue verwantskappe vas te stel tussen inligting wat ingewin is met behulp van nuwe tegnologieë wat die variasie in plantstatus monitor, soos multi- en hiperspektrale analise, en inligting wat op grondvlak ingewin is. Hieruit sal dit duidelik wees watter metodes en analises die doeltreffendste is vir in-diepte analises en die bestuur van wingerde binne die konsep van presisie-wingerdkunde. Met inagneming van hierdie aspekte, was die doel van hierdie studie om 'n eksperimentele model daar te stel waardeur afstandswaarneming-tegnologie gebruik kan word om variasie binne wingerde te identifiseer en te klassifiseer deur analises van die oorsake van hierdie variasie en invloede op die plant. Die geteikende eksperimentele model was 'n wingerd met hoogs heterogene bogrondse groei. 'n Lugfoto van die wingerd is bestudeer en gemanipuleer om pixelwaardes te verskaf wat die graad van variasie vir verskillende eksperimentele plotte, wat aan die hand van verskillende plotuitlegte gekies is, te kwantifiseer. Grondtoestande is bestudeer op 'n globale én plotvlak, met uiters hoë pH en lae weerstande in kombinasie met verkeerde grondvoorbereidingspraktyke, wat geïdentifiseer is as die hoofoorsake vir die hoë vlakke van variasie. Grondfisiese en -chemiese toestand is ook tydens profielgatstudies bestudeer. Betekenisvolle verskille is gevind tussen verskeie grondverwante parameters gemeet vir plotte met onderskeidelik laer en hoër groeikrag, en 'n sterk verwantskap is gevind tussen grondweerstand en pixelwaardes, soos vanaf die lugfoto bepaal. Vegetatiewe metings het ook betekenisvolle verskille tussen die hoër en laer groeikragvlakke opgelewer, wat die geskiktheid van die wingerd vir die studie van binnewingerdvariasie in groeikrag bevestig het. Van hierdie metings was ook nou verwant aan grondtoestande, asook beeldpixelwaardes. Stamomtrek was 'n uitstekende maatstaf vir die vlakke van variasie, aangesien dit nou verwant was aan lowertoestande, grondtoestande, asook beeldpixelwaardes. Blaarwaterpotensiaal-metings het ook betekenisvolle verskille tussen die hoër en laer groeikragvlakke opgelewer. Oesdata en wynanalise het die uitwerking van groekragverskille op druifsamestelling en wynkwaliteit uitgewys, selfs al was die verskille wat gevind is minder as wat verwag is. Hoewel geen duidelike voorkeur tussen die wyne afkomstig van verskillende groeikragvlakke uitgewys kon word nie, was die wyn wat van die laer-groeikrag stokke gemaak was, meer vrugtig. Die algemene kwaliteit van beide wyne was egter baie hoog as in ag geneem word dat eksperimentele wynmaakprosedures gevolg is. Hiperspektrale metings het ook die verskille tussen groeikragvlakke bevestig deur 'n nou-bandwydte NDVI ("normalised difference vegetation index"). Dit was ook moontlik om verskille in sekere biochemiese komponente tussen die groeikragvlakke op 'n blaar- én lowervlak uit te wys. Golflengte-areas ooreenstemmend met karotenoïed, chlorofil a en chlorofil b het verskillende spektrale reaksies in die blare met hoër stresvlak (laer groeikrag) lowers ten toon gestel. Dit het moontlikhede vir verdere navorsing uitgewys. Hierdie studie en die resultate wat verkry is, is die eerste van sy soort in die Suid- Afrikaanse wynbedryf. Dit baan die weg vir meer gefokusde en in-diepte analise van die gebruik van spesifiek multispektrale en hiperspektrale data om binne-wingerdgroekragvariasie akkuraat te monitor en te bestuur met die oog op optimum wynkwaliteit vir 'n spesifieke produkdoelwit. Die aanslag van hierdie navorsing is ook sigbaar in ander prominente wynproduserende lande. Beskikbaarheid van wetenskaplike navorsing rakende die optimale gebruik en tekortkominge van hierdie tegnologieë het die potensiaal om produksiebestuurspraktyke in die wingerdbedryf in die komende jare te revolusionaliseer.

Thesis (MSc)--University of Stellenbosch, 2004.
ENGLISH ABSTRACT: Arbuscular mycorrhizal (AM) C-costs in grapevines were investigated. Since both dormant vines and AM colonisation rely on stored C for initial growth, AM colonisation costs would therefore compete with plant growth for available C reserves. The aims of this study were to assess the host C economy during AM development and the subsequent C-costs of N and P uptake, as well as the effects of C costs on host growth. This was evaluated in two separate experiments; one assessing the symbiotic influence on the C costs of fungal establishment and nutritional benefits, whilst the other one evaluated the effects of the symbiosis on host growth and nutrient productivities. This study has shown that AM acts as a C sink, competing with the host for available C. Past work on the AM sink effect has focused mainly on the movement of photosynthetic C below ground to support the AM fungus. This however, does not take into account the effect that stored C will have on the C economy of the plant and symbiosis. The role of stored C becomes even more crucial when working with deciduous plants that rely on stored C for new growth at start of a growing season. It has been reported that stored C in AM plants is remobilized at the start of a growing season and then the C reserves are refilled towards the end of the season, when the plants enter dormancy. The initial costs of AM fungal colonisation were borne by the above-ground C reserves, at the expense of new growth in host plants. These costs were offset once the plateau phase was reached, and the depleted reserves started to refill. Once established, the active symbiosis imposed a considerable below ground C sink on host reserves. In spite of these costs, the improved P nutrition of AM roots was achieved with a more efficient C-use. This concurs with other findings, that of the belowground C allocated to AM roots, a greater part is used by AM respiration and a smaller part for P uptake. The C costs of the AM fungal phase of rapid development can be seen as negative to root growth and shoot development. These negative effects may continue for a period of time, even during the plateau phase of fungal development. Once the AM symbiosis is fully established, the host growth and development is then improved to a greater extent than in non-AM plants. From this study it can be concluded that AM growth directly competes with host development, but the symbionts revert to a beneficial partnership once it is fully established.
AFRIKAANSE OPSOMMING: Die C koste van arbuskulêre mikorisa (AM) in wingerdstokke is ondersoek. Beide rustende wingerdstokke en AM koloniseering is afhanklik van gestoorde C vir aanvanklike groei. AM kolonisering sou dus met plantgroei kompeteer vir beskikbare C reserwes. Die doelstellings van hierdie ondersoek was eerstens om die C-ekonomie van die gasheer tydens AM ontwikkeling en die gevolglike Ckostes van N en P opname te bepaal en tweedens sowel as die invloed van C veranderings op gasheergroei vas te stel. Hierdie is in twee afsonderlike eksperimente ondersoek: een om die simbiotiese invloed op die C-kostes van swam-vestiging en voedingsvoordele te bepaal, terwyl die ander die uitwerking van simbiose op gasheergroei en voedings doeltreffenheid evalueer het. Die ondersoek het bewys dat AM, as ‘n C-sink, kompeteer met die gasheer vir beskikbare C. Vorige werk oor die AM sink-effek het hoofsaaklik gefokus op die afwaartse beweging van fotosintetiese C om die AM-swam ondergronds te ondersteun. Die werk neem egter nie in ag wat die effek van gestoorde C op die C-ekonomie van die plant en simbiose sou wees nie. Die rol van gestoorde C is selfs nog meer belangrik wanneer met bladwisselende plante gewerk word, omdat sulke plante op gestoorde-C vir nuwe groei aan die begin van die groeiseisoen staatmaak. Dit is op rekord dat gestoorde C in bladwisselende plante by aanvang van die groeiseisoen gemobiliseer word en dat die C-reserwes teen die einde van die seisoen wanneer die plante rustyd nader, weer hervul word. Die aanvanklike kostes van AM kolonisering is deur die bogronds C-reserwes, ten koste van nuwe groei van die gasheerplante, gedra. Hierdie kostes herstel sodra die plato-fase bereik is, waar die uitgeputte reserwes begin hervul het. As die aktiewe simbiose eers gevestig is, sal dit as ‘n onderg P-voeding van AM wortels verkry wordrondse C-sink vir gasheer optree.Hierdie C verbruik word egter as doeltreffend beskou aangesien verbeterde. Dit is bekend dat ‘n groter deel van die ondergrondse C geallokeer word aan AM-wortels, deur middel van AM respirasie en P-opname. Die C-kostes van die AM-fungus tydens die fase van vinnige ontwikkeling, kan ‘n negatiewe effek op wortel- en lootontwikkeling hê. Hierdie negatiewe uitwerking kan vir ‘n tydperk voortdeur, selfs gedurende die plato-fase van fungi-ontwikkeling. Sodra die AM-simbiose volledig gevestig is, word gasheergroei en ontwikkeling tot ‘n groter mate verbeter as in plante sonder AM-fungi. Hierdie ondersoek het bewys dat AM groei direk met gasheerontwikkeling kompeteer, maar dat die simbiose ‘n voordelige vennootskap vorm sodra dit volledig gevestig is.

Two experiments were conducted to detect differences in growth and cold hardiness during establishment of northern grown wine grapevines. One experiment tested the use of four grow tube treatments and two pruning levels on vine establishment in the upper Midwest. The variables included leaf area, stem height, root growth, phenology, and hardiness. Overall, few significant differences occurred among treatments where grow tubes were utilized. In the second season, vines without grow tubes had superior measurements in nearly all leaf area categories. For this reason, it is recommended that growers refrain from grow tube use during establishment in northern growing regions. Vines pruned to three buds after transplanting varied little from those without pruning. For this reason, it is recommended that growers utilize the most efficient early pruning strategy for their particular situation. Another experiment was conducted to determine the effectiveness of different weed control measures. This experiment compared three kinds of mulches and an herbicide treatment on the growth and establishment of four wine grape varieties. Annual weed control, plant growth, phenology, soil water content and temperature, and vine hardiness were measured. Overall, vines receiving mulch had more consistent annual weed control and reduced early season growth when compared to chemically treated vines. For this reason, mulch is recommended in the vineyard for annual weed control during establishment in situations where vigor is not unacceptably low.

Four year old 'Flame Seedless' grapevines, located in a commercial vineyard, were subjected to increased water stress levels based on infrared canopy temperatures and the Crop Water Stress Index (CWSI) for two years. CWSI levels were approximately .18, .30 and .33 for the wet, medium and dry treatments. In the first year there were no significant differences in yield however, there was a significant reduction in the amount of water applied in both the medium and dry treatments when compared to the wet treatment. In addition, the wet treatment had significantly greater growth during the first growing season when comparing pruning weights.

Thesis (MScAgric)--Stellenbosch University, 2012.
ENGLISH ABSTRACT: Phenolic compounds are important quality indicators of a red wine, as they can contribute to the colour of a young red wine, colour stability during ageing as well as astringency, bitterness, body and overall mouthfeel properties. Wine composition is commonly influenced by winemaking and viticultural practices. In South Africa it often happens that vines are excessively vigorous, resulting in canopies that are too dense, which in turn could have a negative effect on the quantity and quality of the grapes produced. Viticultural practices such as judicious canopy management and irrigation are designed to control vine vigour and yield, thus improving fruit ripening and colour development. Artificial shading and water deficit have been reported to have an influence on the sensory properties of red wine as well as on the flavonoid composition. These effects are dependent on a number of factors, however, including the season, cultivar, light intensity, and the extent and timing of water deficit. There is limited research on the possible interactive effects of grapevine water deficits and canopy manipulation on grape and wine flavonoid composition in Shiraz, as well as the relationships between berry and wine composition. We thus investigated the effect of canopy reduction in combination with water deficit on the phenolic and colour composition of Shiraz grapes at different levels of ripeness, and in their corresponding wines after alcoholic and malolactic fermentation as well as after six months’ ageing. This study found that it is possible to improve the phenolic composition of grapes and wine by shoot removal, and some of the tendencies in the wines were also observed after the ageing period. If the shoot removal is not performed at a very early stage, sunburn damage can occur and this will result in berries with a lower mass and volume at harvest due to excessive exposure without the berry having adapted to the imposed conditions. Harvesting at different ripeness levels also affected the chemical and phenolic composition of the grapes and resulting wines. The water deficit effect on most phenolic parameters measured in the grapes and wine was not as prominent as that of the canopy manipulation treatment. This study improved our understanding of how an improvement in the canopy microclimate of Shiraz could be reflected in the phenolic composition of wines, along with a potentially important effect of harvesting date. On this basis it may be possible to attain a specific wine style. Harvesting at a ripe stage, for example, could result in the production of wines with higher colour density and astringency, while unripe grapes could result in wines with higher levels of perceivable fresh berry attributes. In particular, canopy reduction could increase the astringency and body of wines made from grapes subjected to water deficit.
AFRIKAANSE OPSOMMING: Fenoliese verbindings is belangrike kwaliteitsparameters van rooiwyn, aangesien dit kan bydra tot die kleur van ‘n rooiwyn, kleurstabiliteit tydens veroudering sowel as frankheid, bitterigheid en mondgevoel. ‘n Wyn se fenoliese samestelling word algemeen bepaal deur wynmaak- en wingerdkundige praktyke. In Suid-Afrika gebeur dit gereeld dat wingerde uitermatig groeikragtig is, wat lei tot te digte lower wat sodoende ‘n negatiewe effek op kwantiteit en kwaliteit van die druiwe wat geproduseer word, het. Wingerdkundige praktyke soos oordeelkundige lowerbestuur en besproeiing is ontwerp om wingerdstokke se groeikrag en opbrengs te beheer, en sodoende vrugrypwording en kleurontwikkeling te verbeter. Kunsmatige beskaduwing en waterstres is gerapporteer om ‘n invloed te hê op die sensoriese eienskappe van rooiwyn sowel as op die flavonoïedsamestelling. Hierdie effekte is egter afhanklik van ‘n verskeidenheid faktore, insluitende die seisoen, kultivar, ligintensiteit en die mate en tyd van waterstres toegepas. Daar is beperkte navorsing op die moontlike interaktiewe effekte van waterstres en lowermanipulasie op die druif en wyn flavonoïedsamestelling in Shiraz, sowel as die verhoudings tussen druif en wyn samestelling. Ons het dus die effekte van lowerbestuur in kombinasie met waterstres op die fenoliese en kleursamestelling van Shiraz druiwe by verskillende rypheidsvlakke ondersoek, asook in hul ooreenstemmende wyne na alkoholieseen appelmelksuurfermentasie sowel as na ses maande veroudering. Hierdie studie het gevind dat dit moontlik is om die fenoliese samestelling van druiwe en wyn deur lootverwydering te verbeter, en sommige van die tendense is ook waargeneem in die wyn na die verouderingsperiode. Indien lootverwydering nie toegepas word by ‘n baie vroeë stadium nie, kan sonbrand voorkom en dit kan lei tot korrels met ‘n laer massa en volume by oes as gevolg van oormatige blootstelling sonder dat die korrel aangepas het by die spesifieke kondisies. Oes by verskillende rypheidsvlakke affekteer ook die chemiese en fenoliese samestelling van die druiwe en ooreenstemmende wyne. Die waterstreseffek op meeste van die fenoliese parameters gemeet in druiwe en wyn was nie so prominent soos dié van die lowermanipulasie behandeling nie. Hierdie studie het ons begrip verbeter van hoe ‘n verbetering van die lower mikroklimaat van Shiraz gereflekteer kan word op die fenoliese samestelling van die wyn, saam met ‘n potensiële belangrike effek van oesdatum. Op grond van hierdie basis is dit dus moontlik om ‘n spesifieke wynstyl te verkry. Oes by ‘n ryp stadium, byvoorbeeld, kan die produksie van wyn met ‘n hoër kleurdigtheid en frankheid tot gevolg hê, terwyl onryp druiwe wyne met hoër vlakke van waarneembare vars bessiekenmerke tot gevolg kan hê. Verlaging van lowerdigtheid kan veral die frankheid en mondgevoel van wyne gemaak van druiwe blootgestel aan waterstres, verbeter.

Both the physiological and biochemical control of budburst in the grapevine, Vitis Vinifera L. were investigated. It was found that the accuracy of a predictive model for grapevine budburst based on ambient temperature was limited under the experimental conditions. There was a significant correlation of 4.7 ± 0.3 days between the days of maximal xylem exudation and budburst over the 3 years of investigation. The co-relationships between daily xylem exudate volume and a range of environmental parameters were considered. It was found that soil temperature was highly correlated against daily xylem exudation. Ambient temperature and soil moisture were significantly correlated with xylem exudation, however the coefficients of correlation were much lower than that of soil temperature. Rainfall showed only a very limited correlation with daily xylem exudate flow. Seasonal variations in the pH and the carbohydrate and inorganic nutrient concentrations of xylem exudate were investigated. Exudate carbohydrate concentrations fell from 660 µM before the day of maximal xylem exudation to zero levels within 4 weeks. Xylem exudate pH was found to consistently fall to a minimum at the time of maximal exudate flow. Exudate concentrations of the metallic cofactors Ca, K, Mg, Mn and Zn varied directly with daily exudate flow, suggesting some sort of flow-dependent mobilisation of these nutrients. A growth promontory oligosaccharide fraction was prepared by partial acid hydrolysis of grapevine primary cell wall material. This fraction significantly increased control growth of the Lemna minor L. bioassay over a limited ‘window’ of bioactivity. A growth inhibitory oligosaccharide fraction, similar in activity to abscisic acid was isolated from grapevine xylem exudate prior to budburst. The exudate concentration or efficacy of this substance declined after budburst such that there was no apparent growth inhibition. A model is proposed for grapevine budburst whereby an oligosaccharide growth inhibitor is gradually removed from the xylematic stream under the effects of soil temperature, allowing the surge of metabolic activity and vegetative growth that constitute budburst.

Thesis (PhD) -- Stellenbosch University, 1991.
ENGLISH ABSTRACT: The effect of partial defoliation as canopy management practice on metabolism and grape composition of the grapevine, Vitis vinifera L cv. Cabernet Sauvignon, was investigated. The establishment of physiologically sound principles on how to overcome deleterious effects associated with vigorous and dense-canopy vines is emphasized. Experimental vines were defoliated 33 % and 66 % evenly over the whole canopy from different developmental stages in a field study. Effects on canopy microclimate, photosynthesis, photosynthate translocation, vegetative growth, reproductive growth, root development and distribution, as well as grape and wine quality, were determined. A method for the simultaneous extraction of sugars and organic acids from freeze-dried berries at different developmental stages is described. Partial defoliation of vines improved canopy microclimate and photosynthetic efficiency of remaining leaves. Normal translocation and distribution patterns of photosynthates were apparently unaffected by partial defoliation. Translocation to and accumulation of photosynthetic products in the leaves and bunches of partially defoliated vines were, however, improved. Remaining leaves of partially defoliated vines were in comparison photosynthetically more active. Apart from a less favourable canopy microclimate, it seemed that the sink capacity of non-defoliated vines did not comply to the source capacity, inducing a reduced rate of photosynthesis. Normal sigmoidal growth patterns of vines were not affected by partial defoliation as applied in this study. This is important for the longevity, healthiness and productivity of vines. Vegetative growth was differentially affected by partial defoliation. No compensatory leaf growth occurred in reaction to partial defoliation from different developmental stages. Main shoot length, however, decreased slightly. Lateral shoot length and number of laterals increased, whereas cane mass decreased when vines were partially defoliated, particularly the earlier and more severe the defoliation. Reproductive growth in terms of yield was deleteriously affected by 33 % defoliation prior to pea size and 66 % defoliation prior to veraison. Budding percentage was, however, improved by 33 % and 66 % defoliation, whereas bud fertility was only improved by 33 % defoliation. Partial defoliation changed the canopy microclimate to conditions favourable for pest and disease control and higher grape quality. Subterranean growth was favourably affected by partial defoliation, particularly when applied from pea size stage. These changes included higher root densities, development of higher numbers of fine and medium diameter roots and occurrence of higher total root numbers in all soil layers. Generally, defoliations from pea size and veraison were more efficient regarding root development than defoliations from just after bud break and from berry set. Partially defoliated vines reacted by forming new roots, creating a more efficient nutrient absorption capacity and utilization of soil and available water and that, together with higher photosynthetic activities of leaves, provided an efficient mechanism for continued high performance. Grape quality was not affected markedly by partial defoliation. Total soluble solids in berries of defoliated vines were comparable to and even significantly higher than those of non-defoliated vines in some cases, in spite of much lower leaf areas. Generally, total titratable acidity of musts was also slightly higher for partially defoliated vines. Glucose and fructose concentrations in berries were unaffected by partial defoliation, while tartaric acid concentrations were slightly increased and malic acid concentrations slightly decreased. Partial defoliation generally increased the anthocyanin concentration of berry skins. These changes in grape composition suggest higher grape quality and seemed to result from improved light conditions in the canopy interior. Berry volume decreased with partial defoliation, which lowered the pulp:skin ratio. These berries are more desirable for quality wines. Regardless of severity or the developmental stage defoliation was commenced, wine cultivar character and overall wine quality were significantly improved. Partial defoliation changed the general metabolism of vines, mainly in terms of more favourable source:sink ratios, resulting in more efficient photosynthesis, subterranean performance and canopy microclimate. In general, the results suggest that an even removal of 33 % of leaves opposite and below bunches during the period from flowering or berry set to pea size stage may be applied. lt is further suggested that existing vigorous and dense-canopy vines be 33 % defoliated evenly on the lower half of the shoot (canopy) from pea size or veraison. This hypothesis proved effective in improving canopy microclimate, photosynthetic activity and yield, while vegetative growth was inhibited. Grape and wine quality were higher. On the whole, partial defoliation as applied in this study, is recommended as canopy management practice in order to facilitate the abolishment of deleterious effects of excessive vegetative growth and canopy density on balanced metabolic activity, fruit and wine quantity and quality, as well as longevity and healthiness of grapevines.
AFRIKAANSE OPSOMMING: Die invloed van blaarverwydering as loofbestuurspraktyk op die metabolisme en druifsamestelling van die wingerdstok, Vitis vinifera L cv. Cabernet Sauvignon, is ondersoek. Die vestiging van fisiologies-betroubare beginsels oor hoe nadelige effekte geassosieerd met geil en lower-verdigte wingerde uitgeskakel kan word, word beklemtoon. Proefstokke is in 'n veldondersoek 33 % en 66 % eweredig oor die hele lower vanaf verskillende ontwikkelingstadiums ontblaar. Effekte op lowermikroklimaat, fotosintese, translokasie van fotosintetiese produkte, vegetatiewe groei, reproduktiewe groei, wortelontwikkeling en verspreiding asook druif- en wynkwaliteit is bepaal. 'n Metode vir die gelyktydige ekstraksie van suikers en organiese sure uit gevriesdroogde korrels op verskillende groeistadiums is ontwikkel. Blaarverwydering het lowermikroklimaat verbeter en fotosintetiese doeltreffendheid van oorblywende blare op die stok verhoog. Normale translokasie en verspreidingspatrone van produkte van fotosintese is skynbaar nie deur blaarverwydering befiwloed nie. Translokasie na, en akkumulering van fotosintetiese produkte in die blare en druiwe van gedeeltelik ontblaarde stokke, is egter verbeter. Oorblywende blare van gedeeltelik ontblaarde stokke was fotosinteties meer aktief. Afgesien van 'n ongunstiger lowermikroklimaat, het die sinkkapasiteit van nie-ontblaarde stokke skynbaar ook nie teen die bronkapasiteit opgeweeg nie en is 'n verlaagde tempo van fotosintese verkry. Normale sigmofdale groeipatrone van die stokke is nie deur blaarverwydering befrivloed nie. Dit is belangrik vir langlewendheid, gesondheid en produktiwiteit van stokke. Vegetatiewe groei is differensieel deur blaarverwydering befrivloed. Geen kompenserende blaargroei het in reaksie op blaarverwydering vanaf verskillende ontwikkelingstadiums voorgekom nie. Hooflootlengte was egter effens korter. Sylootlengte en aantal sylote het toegeneem, terwyl lootmassa afgeneem het met blaarverwydering, veral hoe vroeer en strawwer dit toegepas is. Reproduktiewe groei in terme van opbrengs is nadelig befrivloed deur 33 % ontblaring voor ertjiekorrelstadium en 66 % ontblaring voor die deurslaanstadium. Botpersentasie is egter deur blaarverwydering verbeter, terwyl oogvrugbaarheid slegs deur 33 % ontblaring verbeter is. Blaarverwydering het 'n gunstige lowermikroklimaat vir die beheer van plae en siektes en hoer druifkwaliteit geskep. Ondergrondse groei is gunstig deur blaarverwydering befrivloed, veral wanneer toegepas vanaf ertjiekorrelstadium. Hierdie veranderinge het ingesluit hoer worteldigtheid, ontwikkeling van groter hoeveelhede wortels met 'n fyn en medium deursnit en die voorkoms van 'n groter aantal totale wortels in alle grondlae. Blaarverwydering vanaf ertjiekorrel- en deurslaanstadia was in die algemeen meer doeltreffend ten opsigte van wortelontwikkeling as blaarverwydering vanaf net na bot en vanaf korrelset. Gedeeltelik ontblaarde stokke het gereageer deur nuwe wortels te vorm, waardeur 'n meer doeltreffende vermoe tot voedingstofopname en benutting van grand an beskikbare water verkry is. Tesame met hoer fotosintetiese aktiwiteite van die blare is 'n doeltreffende meganisme vir aanhoudende hoe prestasie verkry. Druifkwaliteit is nie aanmerklik deur blaarverwydering beirwloed nie. Totale oplosbare stowwe in druiwe van gedeeltelik ontblaarde stokke was vergelykbaar en selfs betekenisvol hoer as die van nie-ontblaarde stokke in sekere gevalle, ten spyte van die baie laer blaaroppervlakte. In die algemeen was die totale titreerbare suur in die mos van gedeeltelik ontblaarde stokke oak effens hoer. Glukose- en fruktosekonsentrasies in die druiwe is nie deur blaarverwydering beinvloed nie. Die konsentrasie wynsteensuur is egter effens verhoog en die appelsuurkonsentrasie effens verlaag. Antosianienkonsentrasie van korreldoppe is in die algemeen deur blaarverwydering verhoog. Hierdie veranderinge in druifsamestelling dui op hoer druifkwaliteit en is skynbaar die resultaat van verbeterde ligtoestande in die binnekant van die lower. Korrelvolume het afgeneem met blaarverwydering. Dit het die pulp:dop verhouding verlaag. Sulke korrels is meer gewens vir bereiding van kwaliteitswyne. Wyn cultivarkarakter en totale wynkwaliteit is betekenisvol deur blaarverwydering verhoog, onafhanklik van die strafheid of ontwikkelingstadium waarvandaan blare verwyder is. Blaarverwydering het die algemene metabolisme van die wingerdstok verander, hoofsaaklik ten opsigte van meer gunstige bron:sink-verhoudings en derhalwe meer doeltreffende fotosintese, ondergrondse groei en lowermikroklimaat. Die resultate dui in die algemeen daarop dat 'n eweredige blaarverwydering van 33 % regoor en onderkant die trosse tydens blomvorming of korrelset tot ertjiekorrelstadium toegepas kan word. Die resultate dui verder daarop dat 33 %van bestaande geil en lower-verdigte stokke se blare eweredig verwyder kan word op die onderste helfte van die loot (lower) vanaf ertjiekorrel- of deurslaanstadium. Hierdie hipotese was suksesvol in die verbetering van lowermikroklimaat, fotosintetiese aktiwiteit en oesmassa. Vegetatiewe groei is gestrem. Druif- en wynkwaliteit was hoer. In die geheel kan blaarverwydering soos toegepas in hierdie ondersoek aanbeveel word as loofbestuurspraktyk ten einde die uitskakeling van nadelige effekte van oormatige vegetatiewe groei en lowerdigtheid op gebalanseerde metaboliese aktiwiteit, druif- en wynkwantiteit en kwaliteit, asook langlewendheid en gesondheid van wingerdstokke te bevorder.

Thesis (PhD(Agric))--Stellenbosch University, 2012
ENGLISH ABSTRACT: Field spectroscopy was used to study leaf composition and selected factors (including canopy growth manipulation and water status changes) that may impact on it in a Vitis vinifera cv. Shiraz vineyard, showing considerable variability in vigour. Temporal and spatial variability in leaf composition were incorporated into measurements by analysing leaves in different shoot positions and at different developmental stages during three different growing seasons. Irrigation and canopy manipulation treatments were also imposed in order to provide new insights into assessing the grapevine leaf and possibly also the canopy growth and ageing dynamics as well as pigment content, as a basis of executing a generally non-destructive measurement approach. Despite large climatic differences between the seasons, canopy size seemed of crucial importance in determining grapevine water relations in the grapevines from the different canopy manipulation treatments. Drastic compensation effects in terms of secondary shoot growth also followed the canopy reduction treatment. Despite this, canopy microclimate was apparently improved, considering the results from light measurements as well as the ripening dynamics in the reduced canopies. Reduced canopies also seemed to display a different canopy composition, in favour of secondary growth. This could have impacted positively on water use efficiency as well as ripening, due to higher photosynthetic efficiency of these leaves during the ripening stages. The reduced canopy treatments offered the possibility of attaining technological ripeness at an earlier stage and at comparatively lower potential alcohol levels. This study illustrated the relevance of considering the vegetative development of the grapevine, along with leaf ageing in the canopy, when conducting calibrated non-destructive measurements of leaf pigments, structure and water content. The relevance of using multivariate techniques in leaf spectroscopy was shown. This can be applied and simplified to aid in non-destructive leaf pigment, structure and water content estimation in future studies. Even with the general variation encountered in this vineyard, predictions of the major pigments in grapevine leaves were within acceptable error margins. Further work is required to improve the modelling of xanthophylls, which may require non-linear multivariate techniques. Logistical shoot growth modelling was used in leaf age estimation and classification, which made it possible to simplify statistical analysis of the leaf parameters mentioned. Practical application of the modelled and predicted parameters was shown for a specific period in season two by comparing the reaction of different treatments to developing water deficits. The results indicated that several parameters, with special mention of the carotenoid:chlorophyll ratio and chlorophyll a:b ratio, can be monitored on young and old leaves in the canopy in order to monitor developing water deficit stress. The modelled parameters, however, did not seem to be sensitive enough to allow specific prediction of predawn leaf water potential values. Specific leaf mass, equivalent water thickness, total specific leaf mass as well as leaf chronological age were successfully predicted from leaf spectral absorbance data, and this may be useful in future work on quantifying leaf adaptation to the micro-environment within the canopy.
AFRIKAANSE OPSOMMING: Veldspektroskopie is gebruik om blaarsamestelling en spesifieke faktore (insluitend lowergroei manipulasie en waterstatus veranderinge) wat ‘n impak kan hê in ‘n Vitis vinifera cv. Shiraz wingerd, met beduidende variasie in groeikrag, te ondersoek. Ruimtelike, asook tydsgebonde, variasie in blaarsamestelling is geïnkorporeer in die metings deur blare van verskillende lootposisies en vir verskillende ontwikkelingstadia gedurende drie verskillende groeiseisoene te meet. Besproeiings- en lowermanipulasie behandelings is ook uitgevoer om die dinamiek van blaar- en lowergroei, veroudering, asook pigmentinhoud te bestudeer binne die konteks van die uitvoering van ‘n nie-destruktiewe meetstrategie. Ondanks groot klimaatsverskille tussen die seisoene, blyk lowergrootteverskille belangrik te wees in die bepaling van wingerdstok-waterverhoudings in die verskillende lowermanipulasie behandelings. Drastiese kompensasiereaksies ten opsigte van sylootgroei is waargeneem in reaksie op die gereduseerde lowerbehandeling. Indien die resultate van ligmetings en druifrypwording in die gereduseerde lowerbehandeling in ag geneem word, is lowermikroklimaat egter steeds verbeter. Hierdie behandeling het oënskynlik ook veranderde lowersamestelling gehad, tot voordeel van sylootgroei. Dit kon moontlik ‘n positiewe invloed gehad het op waterverbruikseffektiwiteit asook druifrypwording, as gevolg van moontlike hoër fotosintetiese effektiwiteit van die blare gedurende die rypwordingstadia. Die gereduseerde lowerbehandeling het die moontlikheid gebied om tegnologiese rypheid by ‘n vroeër datum te bereik, met moontlike laer alkoholvlakke in die wyn. Hierdie studie het die belangrikheid beklemtoon om die vegetatiewe ontwikkeling van die wingerdstok in ag te neem wanneer gekalibreerde nie-destruktiewe metings van blaarpigmente, blaarstruktuur asook waterinhoud onderneem word. Die belang van multi-variant meettegnieke in blaarspektroskopie is aangetoon. Dit kan verder vereenvoudig word ter ondersteuning van niedestruktiewe meting van blaarpigment, -struktuur en -waterinhoudsbepaling in toekomstige studies. Selfs met die variasie wat in die wingerd voorgekom het, was die voorspellings van die vlakke van die belangrikste pigmente wat in wingerdblare aangetref word binne aanvaanbare foutgrense. Opvolgwerk is nodig om die modellering van xanthofil te verbeter, aangesien dit moontlik nielineêre multi-variant analise mag benodig. Logistiese groeimodellering is gebruik om blaarouderdom te bepaal en te klassifiseer, wat dit moontlik gemaak het om statistiese analise te vereenvoudig vir die genoemde blaarparameters. Die praktiese toepassing van die gemodelleerde en voorspelde parameters is aangetoon vir ‘n spesifieke gedeelte in seisoen twee, deur die reaksie van verskillende behandelings op toenemende watertekorte te bestudeer. Resultate het aangetoon dat verskeie parameters, met spesifieke klem op die karotenoïed:chlorofil verhouding, asook die chlorofil a:b verhouding, gemoniteer kan word op jong en ouer blare in die lower ten einde ontwikkelende waterstrestoestande te identifiseer. Die gemodelleerde parameters was egter klaarblyklik nie sensitief genoeg vir akkurate voorspelling van voorsonsopkoms-waterpotensiaalvlakke nie. Spesifieke blaarmassa, ekwivalente waterdikte, totale spesifieke blaarmassa, sowel as blaarouderdom kon suksesvol voorspel word deur gebruik te maak van absorpsieblaarspektroskopie, wat nuttig kan wees in toekomstige studies wat handel oor die kwantifisering van blaaraanpassing by die mikro-omgewing binne ‘n wingerdlower.

Thesis (MScAgric (Viticulture and Oenology))--University of Stellenbosch, 2010.
ENGLISH ABSTRACT: Because of long-term climate changes, apparently associated with higher temperatures and fewer rainfall events, factors such as water-use efficiency and site selection for new cultivars are a matter of increasing importance for viticulture. Within this context, the root system is expected to play a key role. Its relevance to grapevine functioning is due to the numerous functions in which it is involved. In the light of this, the development of the root system is highly relevant to the viticulturist because of the fact that grapevine growth and functioning are dependent on the development of the root system. Differences can, therefore, be expected in terms of berry ripening on single grapevines of the same scion for situations with differing development of root systems, despite being grafted on the same rootstock. Root growth is influenced by several factors, among the ecological aspects. Soil parameters have a predominant influence on root growth and distribution but also annual root production can be altered by canopy manipulation. Due to the importance of root growth to the aboveground development of the vine, it is critical to gain understanding of the relationship between soil factors and root growth and distribution, and the central role that the subterranean environment plays in the concept of terroir. This study aimed to investigate the effect of selected soil physical and chemical parameters on root growth and distribution and to investigate whether having very different canopies influences root growth. In order to achieve these goals, two experiments were conducted; the first was performed in two commercial Sauvignon blanc vineyards each grafted onto Richter 110, non-irrigated, with two treatments: undisturbed lateral growth and complete lateral removal. The second study included the analysis of eight commercial Sauvignon blanc vineyards grafted onto Richter 99 and Richter 110 located in the Stellenbosch Wine of Origin District. Measurements of physical and chemical soil parameters, root growth and distribution, canopy growth and functioning, vine water status and berry composition were performed. The edaphic factors appeared to be one of the most important parameters that affected root development by changing soil water availability and possibly causing physical or chemical limitations on root growth. From the results of this study, it is clear that severe water stress and a pH (KCl) lower than 4.5 play a key role in the limitation of root growth. Due to the fact that most of the soils from the Stellenbosch Wine of Origin District, especially the subsoils, are acidic, this is a factor to consider before planting. On the other hand, the combination of favourable edaphic conditions, such as a subsoil pH of higher than 5.0, light- to mediumtextured subsoil and moderate water stress, allow increased growth of thin roots. However, the effect of canopy management on root growth cannot be discounted due to its importance in the variation of carbohydrate demand by competing sinks. This study showed that lateral removal done from when the berries are at pea size results in an increase in the number of thin roots (0.5-2.0 mm). The secondary leaf area represents at least the same leaf area as the primary leaf area in all the vineyards evaluated, which reveals the relative importance of the laterals in the total leaf area of the vine and the potential importance in terms of microclimate and leaf area available for photosynthesis. Studies of root growth should take the vineyard canopy architecture into account.
AFRIKAANSE OPSOMMING: As gevolg van langtermyn klimaatsveranderinge wat toegeskryf kan word aan die voorkoms van hoër temperature en laer reënval, is faktore soos effektiwiteit van waterverbruik en liggingseleksie vir nuwe kultivars van kardinale belang vir wingerdkunde. Binne hierdie konteks, speel die wortelsisteem ‘n belangrike rol. Die belangrikheid hiervan vir wingerdfunksionering kan toegeskryf word aan die talle funksies waarby dit betrokke is. Die ontwikkeling van die wortelsisteem is dus hoogs relevant vir die wingerdkundige, omdat wingerdgroei en funksionering afhanklik is van die ontwikkeling van die wortelsisteem. Verskille kan daarom dus verwag word in terme van korrelrypwording op ‘n enkele wingerdstok van dieselfde onderstok vir gevalle met verskillende ontwikkeling van die wortelsisteem, ten spyte daarvan dat dit op dieselfde onderstok geënt is. Wortelgroei word, onder ekologiese aspekte, deur verskillende faktore beïnvloed. Grondfaktore het meerendeels ‘n predominante invloed op wortelgroei en -verspreiding, terwyl jaarlikse wortelproduksie deur lowermanipulasie beïnvloed kan word. Weens die belangrikheid van wortelgroei vir die bogrondse ontwikkeling van die wingerd, is dit krities om kennis op te doen oor die verhouding tussen grondfaktore en wortelgroei en –verspreiding, asook die sentrale rol wat die subterreinomgewing op die terroir-konsep speel. Die studie was daarop gemik om die invloed van geselekteerde fisiese en chemiese parameters van grond op wortelgroei en -verspreiding vas te stel, en ook te ondersoek of verskillende lowers wortelgroei sal beïnvloed. Om laasgenoemde doelwitte te bereik, is twee eksperimente uitgevoer. Die eerste is uitgevoer in ‘n kommersïele Sauvignon blanc-wingerd wat geënt is op Richter 110, sonder besproeïng en met twee behandelings, naamlik onversteurde sêkondere lootgroei en volledige sêkondere lootverwydering. Die tweede studie het die analise van agt kommersïele Sauvignon blancwingerde geënt op Richter 99 en Richter 110 in die Stellenbosch Wyn van Oorsprong Distrik. Metings van fisiese en chemiese grondfaktore, wortelgroei en -verspreiding, lowergroei en -funksionering, plantwaterstatus en korrelsamestelling is uitgevoer. Dit blyk dat edafiese faktore een van die belangrikste parameters is wat wortelontwikkeling beïnvloed deur beskikbaarheid van grondwater te verander, en wat moontlik fisiese en chemiese beperkings op wortelgroei kan veroorsaak. Uit die resultate van die studie is dit duidelik dat intense waterspanning en ‘n pH (KCl) laer as 4.5 ‘n belangrike rol in die beperking van wortelgroei speel. Aangesien die meeste van die grondsoorte in die Stellenbosch Wyn van Oorsprong Distrik, veral al die subgronde, suur is, is dit ‘n faktor wat in oorweging geneem moet word voor aanplantings. Die kombinasie van gunstige edafiese toestande, soos ‘n subgrond met ‘n pH hoër as 5.0, ‘n lig tot medium tekstuur en matige waterspanning, sal dus aanleiding gee tot ‘n toename in die groei van dun wortels. Die effek van lowerbestuur op wortelgroei kan egter nie buite rekening gelaat word nie weens die belangrikheid daarvan in die variasie van koolhidraataanvraag deur kompeterende vraagpunte. Hierdie studie toon dat, indien sêkondere lootverwydering tydens ertjiekorrelgrootte toegepas is, dit aanleiding gee tot ‘n toename in die dun wortels (0.5 tot 2.0 mm). Die sêkondere blaaroppervlakte verteenwoordig minstens dieselfde blaaroppervlakte as die primêre blaaroppervlakte in al die wingerde wat ondersoek is, wat dui op die belangrikheid van sêkondere lote in die totale blaaroppervlakte van die wingerd en die potensiële belangrikheid daarvan in terme van mikroklimaat en blaaroppervlakte wat vir fotosintese beskikbaar is. Studies van wortelgroei moet lowerargitektuur in ag neem.

Thesis (MScAgric (Viticulture and Oenology))--University of Stellenbosch, 2010.
ENGLISH ABSTRACT: Cabernet Sauvignon is the most planted red cultivar in South Africa and the second most planted red cultivar in the Olifants River region. The cultivar is prone to vigorous growth with low yields. Excessive irrigation could accentuate these cultivar characteristics. Considering the foregoing, the aim of the study was to describe how Cabernet Sauvignon will react to climate, soil type (texture) and irrigation within the Lower Olifants River wine region to enable growers to make the right decisions regarding long term as well as short term cultivation practices. This study is part of a project carried out by the ARC Infruitec-Nietvoorbij at Stellenbosch to determine the effects of soil type and atmospheric conditions on yield and wine quality of Cabernet Sauvignon in different grape growing regions of South Africa. Similar studies are being carried out in the Orange River, Stellenbosch and Swartland regions of South Africa. The Lower Olifants River region could be divided into three climatic regions. Furthermore, two climatic regions is evident regarding the formation of grape wine colour and aromas. Proximity to the Atlantic Ocean would play an important role in a cultivar establishment policy. The variation in stem water potential (ΨS) could be related to soil water status expressed in terms of matric potential (ΨM). In the case of sandy soils, ΨS decreased substantially more as the ΨM decreased compared to the sandy loam soils. The reason could be that the unsaturated hydraulic conductivity in sandy soils decreased more rapidly as the ΨM decreased compared to the heavier soils. Thus could explain why the grapevines in the sandy soils experienced more water stress than the ones in the sandy loam soils at a given ΨM. Climate had a strong influence on grapevine water status with grapevines nearer to the ocean experiencing less water stress compared to the ones further inland. This was especially true for grapevines in the sandy soils. Vegetative growth and yield of grapevines in the sandy soils were more sensitive to water deficits compared to the ones in the sandy loam soils. For deficit irrigated grapevines in the sandy soils, vegetative growth and yield decreased by ca. 30% when ca. 55% less water was applied from flowering to harvest. Yield reduction were ca. 15% with no or very little influence on vegetative growth with ca. 80% reduction in water applied from flowering to harvest for grapevines in the sandy loam soils. The influence of soil texture on wine quality and style were evident under intensive irrigation as well as over different climatic regions. Overall sensorial potential wine quality of grapevines in sandy soils tended to be higher compared to the ones in the sandy loam soils. Deficit irrigation tended to increase wine colour intensity, irrespective of soil texture. Furthermore, deficit irrigation in sandy loam soils tended to increase wine fullness and the berry characteristics of the wine. Berry characteristics of wines from the sandy soils tended to be higher compared to the ones from the sandy loam soils. Too severe water deficits in sandy soils could be detrimental to wine quality. Climate tended to have an influence on wine style of grapevines in the sandy soils with wines produced further away from the ocean tended to have higher berry characteristics. Irrigation management could be a powerful tool to manipulate the grapevine in sandy soils. For grapevines the sandy loam soils in addition to regulated deficit irrigation, additional canopy management practices could be needed to improve wine quality.
AFRIKAANSE OPSOMMING: Cabernet Sauvignon is die mees aangeplante rooidruif kultivar in die Suid-Afrikaanse wynbedryf. In die Olifantsriver streek is dit naas Shiraz, die tweede mees aangeplante rooidruif kultivar. Cabernet Sauvignon is bekend as ‘n groeikragtige skaamdraer. Indien oorbesproei word, kan hierdie potensiële nadelige eienskappe nog meer na vore tree. Die doel van die studie is om die invloed van die klimaat, grond en besproeiing op Cabernet Sauvignon se vegetatiewe groei, produksie en wyngehalte in die Benede Olifantsrivier streek te bepaal. Hierdie inligting kan produsente help om ingeligte kortsowel as langtermyn besluite te maak rakende die verbouing van Cabernet Sauvignon. Hierdie studie vorm deel van ‘n breër studie in die Suid-Afrikaanse wynbedryf, gedryf deur die Landbou Navorsingsraad (LNR) Infruitec-Nietvoorbij, Stellenbosch om die invloed van atmosferiese toestande en grond op die produksie en wyngehalte van Cabernet Sauvignon te bepaal. Soortgelyke projekte word uitgevoer in die Oranjerivier, Stellenbosch en Swartland wynstreke. Die Benede Olifantsrivier streek kan verdeel word in drie klimaatstreke op grond van temperatuurdata. In terme van die ontwikkeling van druifkleur en aromas, kan die streek verdeel word in twee klimaatstreke. Die afstand vanaf die Atlantiese Oseaan kan ‘n belangrike rol speel in die ontwikkeling van ‘n kultivarriglynplan vir die streek. Grondwaterstatus, uitgedruk as die matrikspotensiaal (ΨM), kan aanleiding gee tot variasie in middag blaarwaterpotensiaal (ΨS) lesings. Die ΨS van die sand gronde verlaag vinniger soos die ΨM verlaag invergelyke met die sandleem gronde. Dit kan moontlik wees as gevolg van die verskil in die grond onversadigde hidroliese konduktiwiteit. Sand gronde se hidroliese konduktiwiteit verlaag vinniger soos die ΨM verlaag, invergelyke met sandleem gronde. Dit verklaar waarom wingerde in sand gronde by dieselfde ΨM, meer waterspanning ondervind as wingerde in sandleem gronde. Klimaat het ‘n invloed op die waterstatus van die wingerdstok. Wingerde nader aan die see het minder waterspanning ondervind invergelyke met wingerde wat verder in die binneland geleë is. Dit was veral die geval met wingerde in die sand gronde. Vegetatiewe groei en produksie van wingerde in die sand gronde is meer sensitief vir waterspanning as wingerde in die sandleem gronde. Tekortbesproeiing in die sand gronde het die groei asook produksie met ongeveer 30% verlaag deur ongeveer 55% minder water toe te dien vanaf blom tot oes. In teenstelling daarmee is die produksie van wingerde in die sandleem gronde met ongeveer 15% verlaag met geen tot baie min verlaging in die groeikrag. Ongeveer 80% minder water is toegedien vanaf blom tot oes. Grondtekstuur kan wyngehalte en -styl beïnvloed ten spyte van intensiewe besproeiing en klimaatsverskille. Sensoriese potensiële wyngehalte van wingerde in die sand gronde was beter invergelyke met dié van die sandleem gronde. Die wyne vanaf die sand gronde het ook geneig om oor meer bessie intensiteit te beskik as wyne vanaf die sandleem gronde. Tekortbesproeiing neig om die wynkleur intensiteit te verhoog, ongeag van grondtekstuur. Tekortbesproeiing in die sandleem gronde kan ook die volheid van die wyne verbeter, asook die bessie intensiteit van die wyn verhoog. Te hoë waterspanning in die sand gronde kan wyngehalte nadelig beïnvloed. Klimaat kan ook die wynstyl vanaf sand gronde beïnvloed met wyne verder vanaf die see wat oor meer bessie intensiteit beskik as wyne nader aan die see. Beheerde tekortbesproeiing kan as ‘n kragtige hulpmiddel gebruik word om wingerde in die sand gronde te manipuleer. Vir wingerde in die sandleem gronde, addisioneel tot beheerde tekortbesproeiing en normale loofbestuurspraktyke, kan ekstra loofbestuurspraktyke bv. die verwydering van sylootlote, dalk nodig wees om wyngehalte te verbeter.

Thesis (MScAgric (Viticulture and Oenology))--University of Stellenbosch, 2010.
ENGLISH ABSTRACT: Grapevine water status is considered to be the most important factor limiting plant growth and production in the Mediterranean zones. In these regions with limited summer rainfall and limited water resources for irrigation grapevines may experience water deficits for an extended period of time. The demand of water for agriculture is constantly increasing, and will continue to do so due to the rise in the world population and to the effects of climate change on rainfall and evaporative demand in these regions. The Western Cape wine region is also classified as Mediterranean and grapevines grown in this region are often exposed to water “stress” conditions due to high evaporative demand and low water availability in the soil. Plant water status of grapevines may dependent on, amongst other factors, the water potential of soil layers close to the root system, canopy size and evaporative demand. The canopy size of a grapevine can inherently be seen as a measure of grapevine vigour, and vigour variation among grapevines within a vineyard is a common phenomenon in the Western Cape. The importance of the contributions from several factors causing vigour variation within vineyards is still a subject of debate. This may be largely ascribed to the significant amount of variability in vineyards that researchers have to deal with during viticultural studies. However, the recent advances in remote sensing technology have established new methods to assess grapevine vigour variability. In the face of the recognized variation within vineyards and the importance of a sustained grapevine water status, for wine grape productivity and -quality, it is alarming to think that a vineyard block is generally managed as a homogeneous entity when it comes to irrigation scheduling. What is more alarming is the assumption that grape, juice and wine quality will be homogeneous throughout a vineyard block – even without irrigation. With this in mind, a study was conducted to study the interaction between grapevine vigour and grapevine water status within a commercial vineyard with variable vigour by implementing various irrigation regimes. Vigour variation was identified through multispectral aerial imagery and plant-based water status determinants were used to assess grapevine water status in plots of differing vigour within the vineyard. Soil water status was also assessed, and vegetative growth quantified to ultimately determine the variability in vigour and its possible contribution to the variability through the water status of the plant. Reproductive growth was monitored continually before evaluating the effect of water status and grapevine vigour on grape composition and subsequent wine quality. The various methods used to evaluate grapevine vigour showed good correspondence. Pruning mass measured at the end of the season confirmed leaf area measurement (main leaves and lateral leaves) during vegetative growth, and corresponded well, in terms of main vigour classifications with the NDVI images collected. Berry weight and volume responded to the various classifications, with a decrease in water deficits from one classification to the next accompanying an increase in berry weight and volume. Analyses of the berry composition and wines showed statistically significant differences between the classifications. This was found for sugar content per berry, total phenols, total red pigment, malic acid, nitrogen and pH for the grape juice analyses. Wine pH and total acidity also differed significantly.
AFRIKAANSE OPSOMMING: In die Mediterreense sones word plantwaterstatus beskou as `n hooffaktor wat groei en produksie van `n wingerdstok negatief beinvloed. In hierdie sones kan wingerdstokke vir lang periodes `n tekort aan water ervaar a.g.v `n tekort aan reënwater gedurende die somer en lae beskikbaarheid van besproeingswater. Die vraag na water vir landbou is ook konstant besig om toe te neem in dié sones en die tendens sal voorduur a.g.v die groei in die wêreldbevolking, die effek van klimaatsveranderig op reënvalpatrone en die hoë verdampingsfaktor. Die wingerd- en wynstreek van die Wes-Kaap word ook geklassifiseer as Mediterreens en wingerdstokke in hierdie streek ervaar dikwels waterspanning wat deur hoë evapotranspirasie en min beskikbare grondwater veroorsaak word. Van die faktore wat die waterstatus van `n wingerdstok bepaal is onder andere die waterpotensiaal van die grondlae rondom die wortelstelsel, die grootte van die wingerdlowerraamwerk en die evapotranspirasiebehoefte. Die omvang van `n wingerdstok se lower binne die prieel word beskou as `n aanduiding van wingerdstokgroeikrag en variasie in groeikrag tussen wingerdstokke is `n algemene verskynsel in die Wes-Kaap. Die rangorde, wat die effek van die verskeie faktore wat groeikragvariasie tussen wingerdstokke bepaal, word steeds gedebatteer. Die debat kan groottendeels toegeskryf word aan die beduidende hoeveelheid variasie tussen wingerde waarmee navorsers te doen kry in wingerdkundige studies. Hoewel, met onlangse vordering aangaande afstandswaarnemingstegnologie is daar nou nuwe metodes beskikbaar om wingerdgroeikrag te evalueer. Dit is kommerwekend om te dink dat `n wyndruifwingerd normaalweg as `n homogene eenheid bestuur word as dit kom by besproeiing. Veral met die wete dat groeikragvariasie tussen wingerde algemeen erken en aangeteken word, en dat volhoubare waterstatus van `n wingerdstok van kardinale belang is vir produksie en kwaliteit van wyndruiwe. Die aanname dat wyndruiwe, die sap- en ook wynkwaliteit homogeen sal wees regdeur `n wingerdblok is egter meer kommerwekkend. Na aanvang van dié denke is daar `n studie geloods om die interaksie tussen wingerdstokgroeikrag en wingerdstokwaterstatus te evalueer. Met die studie is verskeie besproeiingsregimes aangebring binne `n kommersiële wingerd wat interne groeikragvariasie tentoonstel. Groeikragvariasie was geïdentifiseer deur middel van multispektrale lugfotos terwyl die wingerdstok se waterstatus geëvalueer is met behulp van plantgebaseerde metings in die verskillende groeikragareas. Die waterstatus van die grond is geëvalueer tesame met die vegetatiewe groei van die wingerd sodat die groeikragvariasie en die invloed van die plantwaterstatus op die groeikrag bepaal kon word. Die reproduktiewe groei is deurlopend gemonitor voor die effek van wingerdstokwaterstatus en wingerdstokgroeikrag op druifsamestelling en wynkwaliteit bepaal is. Daar was `n goeie ooreenkoms tussen die verskeie metodes wat gebruik is om wingerdgroeikrag te bepaal. Snoeimassa aan die einde van die seisoen was ooreenkomstig met die blaaroppervakte (hooflootblare en sylootblare) wat tydens vegetatiewe groei gemeet is, en het ook goed korreleer, met die multispektrale lugfotos se hoof groeikragklassifikasie. Korrelgewig en -volume het reageer op die verskeie besproeiingsregimes, en daar was `n toename in korrelgewig en -volume saam met die afname in watertekort van een regime tot `n ander. Daar was beduidende verskille tussen die verskeie klassifikasies t.o.v. korrelsamestelling analise en wynevaluasie. Die suikerinhoud per korrel, totale fenole, totale rooi pigment, appelsuur, stikstof en pH het verskil in druiwesap analises. Die pH en suur van die wyne het ook beduidend verskil.

Thesis (MScAgric (Viticulture and Oenology))--University of Stellenbosch, 2010.
ENGLISH ABSTRACT: Within-vineyard variability in vigour and water status commonly occurs in South African vineyards. Different soil types found over short distances are probably the main cause of vigour variability, while differences in grapevine water status are commonly induced by lateral water flow in the vineyard, blocked irrigation emitters and differences in soil water-holding capacity. These factors can cause heterogeneous ripening and differences in fruit quality between different parts of the vineyard, an aspect that needs to be avoided as far as possible in order to produce quality wines. Measurements of carbon isotope discrimination (CID) have proved to be a tool to assess grapevine physiology in order to study the effects of environmental parameters on leaf carbon dioxide (CO2) gas exchange and stomatal conductance (gs). Grapevine water deficit stress/strain in reaction to these environmental conditions can then be determined by observing the amount of 13C absorbed by plant material after discrimination of 13C has taken place, and this is influenced by the grapevine stress condition and can indicate water-use efficiency. In this study, the variability of grapevine water status and vigour was determined in order to quantify these parameters in different parts of the vineyard. Two separate trials were conducted, the first at Wellington, South Africa, where different irrigation regimes resulted in variability in grapevine water status between plots. The second trial was at Stellenbosch, South Africa, where plots were divided among different vigour classes and irrigation was applied in different quantities for different irrigation treatments. Within-vineyard variability in water status (Wellington and Stellenbosch) and vigour (Stellenbosch) were then quantified and the effects on some grapevine physiological parameters and berry composition were measured. The treatments in the Wellington trial led to differences in grapevine water status, which could be quantified by measurements of stem water potential (SWP) and leaf water potential (LWP). Soil variability also led to differences in grapevine vigour, which were quantified by measurements of pruning mass, leaf area and shoot length. The effect of the variability in grapevine water status on grapevine physiology was assessed by measuring CID, which was the main focus of the study. Other physiological measurements, such as gs and leaf and canopy temperature, were also conducted. The effect of these conditions on grape berry composition was also studied. In the Stellenbosch trial, soil water content, plant water status measurements (SWP, predawn LWP and LWP), physiological measurements (CID and gs) and berry size measurements were used to classify plots into water status treatments (“wet” and “dry” treatments). The effect of vigour differences was analysed separately from these treatments by using pruning mass as a covariate in the statistical analyses. The effect of vigour variability on the measurements was studied by looking at the effect of the covariate on the measurements, while shoot growth rate, shoot length and leaf area measurements were conducted as vegetative growth measurements. Differences in measurements were then studied between the treatments and between the vigour levels of the different plots. In the Wellington trial, plant water status was determined by irrigation, showing increased stress for treatments that received less irrigation. The differences in plant water status then caused differences in grapevine physiology between the treatments, leading to increased gs for increased irrigation. This of course influenced leaf internal CO2 and therefore CID, although CID was also clearly influenced by berry development. Berry size was influenced by irrigation, with larger berries found in wetter treatments, while berry chemical composition was influenced by the irrigation regime, with increased irrigation leading to increased pH and leading to trends showing increased total soluble solids and malic acid, and reduced total and tartaric acid and colour intensity. In the Stellenbosch trial, plots with higher vigour had increased shoot growth rate, longer shoots and increased leaf area, although topping influenced this. Wet treatment vines also showed slightly longer shoots and larger leaf areas. There were differences in soil water content between the wet and dry treatments, and this led to differences in plant water status. Vigour also influenced pre-dawn LWP, especially in the 2007 season, as higher-vigour vines struggled more to rehydrate through the night. Differences in plant water potential led to differences in grapevine physiology, with increased gs for vines from the wet treatment, while higher-vigour vines had slightly increased gs. The differences in gs led to gas exchange differences and therefore differences in CID, meaning that water status and vigour influenced CID. CID measurements illustrated the long term effect of water status on plant physiology, while measurements such as SWP illustrated the short term effects. CID measurements therefore proved to be accumulative over the season, in contrast to SWP measurements that were much more dependent on the current state of grapevine water status. Other physiological measurements showed that wet-treatment vines had higher photosynthetic rates and evapotranspiration and lower leaf temperatures, while higher-vigour vines had slightly increased evapotranspiration and decreased leaf temperatures. Wet-treatment vines had larger berries, while a higher vigour also led to slightly larger berries. Berry composition was influenced by treatment, where wet-treatment vines had increased pH and total soluble solids, while higher-vigour vines had increased juice pH and, in the 2008 season, decreased total soluble solids. Extremely stressed conditions did not show significant effects on plant water potential, but SWP measurements indicated slightly higher stress for the extremely stressed vines and LWP showed slightly less stressed conditions for these vines. Measurements of gs showed slightly lower values for the extremely stressed vines, while measurements of CID showed large significant differences, with the extremely stressed vines having measurements showing high stress. The measurement therefore indicated highly stressed conditions accurately, while other physiological measurements, such as photosynthetic rate, evapotranspiration and leaf temperatures, only showed trends and no significant differences. Measurements of stomatal conductance reacted to plant water status measurements throughout the diurnal measurement days, while CID only reacted slightly with gs changes during these days and was perhaps influenced more by berry chemical composition and development at this early stage of the season. Vigour and water status therefore influenced grapevine physiology, with a more direct effect by water status and an indirect effect by vigour due to microclimatic differences. This also influenced berry composition and therefore quality. In future studies, CID measurements should be done on juice from which organic acids have been removed in order to eliminate the effect of seasonal berry composition on the measurement. Measurements of CID proved to be an integrative, but sensitive, indicator of grapevine stress, especially at the end of the season. It might at best be useful as a post-harvest management tool for producers or grape buyers, especially for irrigation control, as has also been stated by Van Leeuwen et al. (2007).
AFRIKAANSE OPSOMMING: Binne-wingerd variasie in groeikrag en waterstatus is algemeen in Suid-Afrikaanse wingerde. Verskillende grondsoorte wat na aan mekaar voorkom, is seker een van die vernaamste oorsake van variasie in groeikrag, terwyl verskille in wingerdwaterstatus algemeen deur laterale watervloei in die wingerd, verstopte besproeiingspuite en verskille in grond waterhouvermoë geïnduseer word. Hierdie faktore kan aanleiding gee tot heterogene rypwording en verskille in vrugkwaliteit tussen verskillende dele van die wingerd, ‘n aspek wat so ver moontlik vermy moet word om kwaliteitwyne te kan produseer. Die meting van koolstof-isotoopdiskriminasie (KID) is bewys om as gereedskap te kan dien vir die assessering van wingerdfisiologie om die effekte van omgewingsparameters op blaar koolstofdioksied (CO2) - gasuitruiling en stomatale geleiding (gs) te bestudeer. Die stres/stremming as gevolg van ‘n watertekort in die wingerd in reaksie op hierdie omgewingstoestande kan dan bepaal word deur te kyk na hoeveel 13C deur die plantmateriaal geabsorbeer word ná 13C-diskriminasie plaasgevind het, en dít word deur die wingerdstrestoestande beïnvloed en kan ‘n aanduiding verskaf van die doeltreffendheid van waterverbruik. In hierdie studie is die variasie in wingerdwaterstatus en groeikrag bepaal om hierdie parameters in verskillende dele van die wingerd te kwantifiseer. Twee afsonderlike proewe is uitgevoer, die eerste by Wellington, Suid-Afrika, waar verskillende besproeiingsregimes gelei het tot verskille in die wingerdwaterstatus tussen persele. Die tweede proef was by Stellenbosch, Suid-Afrika, waar persele tussen verskillende groeikragklasse verdeel is en besproeiing in verskillende hoeveelhede vir verskillende besproeiingsbehandelings toegepas is. Binne-wingerd variasie in waterstatus (Wellington en Stellenbosch) en groeikrag (Stellenbosch) is toe gekwantifiseer en die effekte op sekere wingerd-fisiologiese parameters en korrelsamestelling is gemeet. Die behandelings in die Wellington-proef het gelei tot verskille in wingerdwaterstatus, wat deur metings van stamwaterpotensiaal (SWP) en blaarwaterpotensiaal (BWP) gekwantifiseer kon word. Grondverskille het ook gelei tot verskille in wingerdgroeikrag, wat deur metings van snoeimassa, blaaroppervlak en lootlengte gekwantifiseer is. Die effek van die variasie in wingerdwaterstatus op wingerdfisiologie is deur metings van KID bepaal wat die hooffokus van hierdie studie was. Ander fisiologiese metings, soos gs en blaar- en lowertemperatuur, is ook gedoen. Die effekte van hierdie toestande op die samestelling van die druiwekorrels is ook bestudeer. In die Stellenbosch-proef is grondwaterinhoud, metings van plantwaterstatus (SWP, voorsonopgang SWP en BWP), fisiologiese metings (KID en gs) en metings van korrelgrootte gebruik om die persele in waterstatusbehandelings (“nat” en “droë” behandelings) te verdeel. Die effek van verskille in groeikrag is apart van hierdie behandelings geanaliseer deur snoeimassa as ‘n kovariaat in die statistiese analises te gebruik. Die effek van groeikragvariasie op die metings is bestudeer deur ondersoek in te stel na die effek van die kovariaat op die metings, terwyl lootgroeitempo-, lootlengte- en blaaroppervlakmetings as metings van vegetatiewe groei uitgevoer is. Verskille in metings tussen die behandelings en tussen die groeikragvlakke van die verskillende persele is toe bestudeer. In die Wellington-proef is plantwaterstatus deur besproeiing bepaal, met verhoogde stres in behandelings waar daar minder besproeiing toegedien is. Die verskille in plantwaterstatus het dan verskille in wingerdfisiologie tussen die behandelings veroorsaak, wat gelei het tot ‘n verhoogde gs in die geval van verhoogde besproeiing. Dit het natuurlik ‘n effek op die interne CO2 van die blaar en dus op KID gehad, hoewel KID ook duidelik deur korrelontwikkeling beïnvloed is. Korrelgrootte is deur besproeiing beïnvloed, met groter korrels in die natter behandelings, terwyl die chemiese samestelling van die korrel deur besproeiingsregime beïnvloed is. Verhoogde besproeiing het pH verhoog en gelei na tendense wat verhoogde totale oplosbare vaste stowwe en appelsuur, en verminderde totale suur, wynsteensuur en kleurintensiteit getoon het. In die Stellenbosch-proef het persele met hoër groeikrag ook verhoogde lootgroeitempo, langer lote en verhoogde blaaroppervlak getoon, hoewel dit deur top beïnvloed is. Wingerdstokke van die nat behandeling het ook effe langer lote en groter blaaroppervlakke getoon. Daar was verskille in grondwaterinhoud tussen die nat en droë behandelings en dit het verskille in plantwaterstatus veroorsaak. Groeikrag is ook deur voor-sonopgang BWP beïnvloed, veral in die 2007-seisoen, aangesien stokke met hoër groeikrag meer gesukkel het om in die nag te rehidreer. Verskille in plantwaterpotensiaal het gelei tot verskille in wingerdfisiologie, met ‘n verhoogde gs vir stokke in die nat behandeling, terwyl stokke met hoër groeikrag ‘n effens verhoogde gs getoon het. Die verskille in gs het gelei tot verskille in gasuitruiling en dus verskille in KID, wat beteken dat waterstatus en groeikrag ‘n invloed op KID het. KID was meer verteenwoordigend van die langtermyneffekte van water status op plantfisiologie, terwyl metings soos SWP die korttermyneffekte weerspieël het. KID metings was dus akkumalatief oor die seisoen, terwyl SWP metings meer ‘n weerspieëling was van die huidige toestand van plantwaterpotensiaal. Ander fisiologiese metings het getoon dat stokke in die nat behandeling ‘n hoër fotosintesetempo en evapotranspirasie sowel as laer blaartemperature ondervind het, terwyl die stokke met hoër groeikrag effe verhoogde evapotranspirasie en verminderde blaartemperature getoon het. Stokke in die nat behandeling het groter korrels gehad, terwyl hoër groeikrag ook effens groter korrels veroorsaak het. Korrelsamestelling is deur die behandelings beïnvloed, met stokke in die nat behandeling wat verhoogde pH en totale oplosbare vaste stowwe getoon het, terwyl stokke met hoër groeikrag verhoogde pH van die sap en verminderde totale oplosbare vaste stowwe (laasgenoemde in die 2008-seisoen) gehad het. Uitermate toestande van stres het geen beduidende effekte op plantwaterpotensiaal getoon nie, hoewel SWP-metings effens hoër stres vir die uitermate gestresde wingerde getoon het en BWP effens minder gestresde toestande vir hierdie stokke getoon het. Metings van gs het effens laer waardes vir die uitermate gestresde stokke getoon, terwyl metings van KID groot noemenswaardige verskille getoon het, met die metings vir die uitermate gestresde wingerde wat hoër stres aangedui het. Dié meting het dus hoogs gestresde toestande akkuraat aangedui, terwyl ander fisiologiese metings, soos tempo van fotosintese, evapotranspirasie en blaartemperature net tendense en nie beduidende verskille aangedui het nie. Metings van stomatale geleiding het dwarsdeur die dae waarop daaglikse metings gedoen is op plantwaterstatusmetings gereageer, terwyl KID net effens met gs-veranderinge op hierdie dae gereageer het en moontlik meer deur die chemiese samestelling en ontwikkeling van die korrel in hierdie vroeë stadium van die seisoen beïnvloed is. Groeikrag en waterstatus het dus wingerdfisiologie beïnvloed, met ‘n meer direkte effek deur waterstatus en ‘n indirekte effek deur groeikrag as gevolg van mikroklimaatsverskille. Dit het ook korrelsamestelling en dus kwaliteit beïnvloed. In toekomstige studies moet KID-metings gedoen word op sap waarvan die organiese sure verwyder is om die effek van seisoenale korrelsamestelling op die meting uit te sluit. Metings van KID is getoon om ‘n integrerende, maar gevoelige, aanduider van wingerdstres te wees, veral aan die einde van die seisoen. Dit is ten beste miskien bruikbaar as naoesbestuursgereedskap vir produsente of druiwekopers, veral vir besproeiingsbeheer, soos ook reeds deur Van Leeuwen et al. (2007) aangedui is.

Finitely generated monomial algebras are studied. the bound in Bergman's description of algebras with GK-dimension 1 is improved and similar techniques are used to establish the equivalence of the periodicities of overlap graphs and Hilbert series coefficients.
Ph. D.

Ce manuscrit de thèse récapitule mes travaux de recherche sur les profils de séparation et de Poincaré. Le profil de séparation est apparu en 2012 dans un l'article fondateur de Benjamini, Schramm et Timár. La définition donnée tirait ses origines dans des travaux antérieurs, dans le domaine du calcul formel : principalement des études de Lipton et Trajan concernant les graphes planaires, et de Miller, Teng, Thurston et Vavasis concernant des graphes d'intersection. Le profil de séparation est maintenant utilisé en théorie géométrique des groupes, mon domaine de recherche, à cause de sa propriété de monotonie par plongements grossiers. Il a été généralisé par Hume, Mackay et Tessera en 2019 en une gamme continue de profils, appelés profils de Poincaré
The goal of this thesis report is to present my research concerning separation and Poincaré profiles. Separation profile first appeared in 2012 in a seminal article written by Benjamini, Schramm and Timár. This definition was based on preceding research, in the field of computer science, mainly work of Lipton and Trajan concerning planar graphs, and of Miller, Teng, Thurston and Vavasis concerning overlap graphs. The separation profile plays now a role in geometric group theory, where my personal interests lies, because of its property of monotonicity under coarse embeddings. It was generalized by Hume, Mackay and Tessera in 2019 to a spectrum of profiles, called the Poincaré profiles

Stress intensity factors' behaviour is studied for long plane cracks interacting with a region of functionally graded elastic material. The region is assumed embedded into a large body treated as a homogeneous elastic continuum. The analysis is limited to small deviations of the graded region's elastic modulus from that of the surrounding body (Poisson's ratio is kept constant) and analytical solutions are sought using a perturbation technique. Emphasis is laid on the case of an infinite strip, which admits a closed form solution. A cosine change of the modulus of elasticity is treated, furnishing the solution for arbitrary variation in the form of a Fourier's expansion. Finite element analysis is subsequently performed for investigating the scope of validity of the analytical solution. The results for a set of finite changes of the elastic modulus are compared with the analytical predictions, and a remarkably wide range of validity is demonstrated. New functions, suitable for non-homogeneous material description, are introduced to approach the case of non-constant Poisson's ratio. The properties and possible applications of these functions are examined.
Godkänd; 1999; 20070320 (ysko)

La première partie de cette thèse vise à introduire de nouveaux modèles de graphes aléatoires rendant compte de l'évolution temporelle des réseaux. Plus précisément, nous nous concentrons sur des modèles de croissance où à chaque instant un nouveau noeud s'ajoute au graphe existant. Nous attribuons à ce nouvel entrant des propriétés qui caractérisent son pouvoir de connectivité au reste du réseau et celles-ci dépendent uniquement du noeud précédemment introduit. Nos modèles de graphes aléatoires sont donc régis par une dynamique markovienne latente caractérisant la séquence de noeuds du graphe. Nous nous intéresserons particulièrement au Stochastic Block Model et aux Graphes Aléatoires Géométriques pour lesquels nous proposons des algorithmes permettant d'estimer les paramètres du modèle. Nous montrons ensuite comment ce travail d'estimation nous permet de résoudre des problèmes de prédiction de lien ou de filtrage collaboratif dans les graphes.L'étude théorique des algorithmes précédemment décrits mobilisent des résultats probabilistes poussés. Nous avons notamment dû recourir à une inégalité de concentration pour les U-statistiques dans un cadre dépendant. Peu nombreux sont les travaux ayant abordé cette épineuse question et l'existant considère des jeux d'hypothèses ne répondant pas à nos besoins. Aussi, la deuxième partie de ce manuscrit sera consacrée à la preuve d'une inégalité de concentration pour les U-statistiques d'ordre deux pour des chaînes de Markov uniformément ergodique. Dans le Chapitre 5, nous exploitons notre résultat de concentration pour les U-statistiques pour apporter de nouvelles contributions à trois domaines très actifs des Statistiques et du Machine Learning.Toujours motivés par des problèmes de prédictions liens dans les graphes, nous nous intéressons dans un dernier chapitre aux procédures d'inférence post-sélection dans le cadre de la régression logistique avec pénalité $L^1$. Nous prouvons un théorème central limite sous la distribution conditionnelle à l'événement de sélection et nous en déduisons des procédures de test et des intervalles de confiance asymptotiquement valides
The first part of this thesis aims at introducing new models of random graphs that account for the temporal evolution of networks. More precisely, we focus on growth models where at each instant a new node is added to the existing graph. We attribute to this new entrant properties that characterize its connectivity to the rest of the network and these properties depend only on the previously introduced node. Our random graph models are thus governed by a latent Markovian dynamic characterizing the sequence of nodes in the graph. We are particularly interested in the Stochastic Block Model and in Random Geometric Graphs for which we propose algorithms to estimate the unknown parameters or functions defining the model. We then show how these estimates allow us to solve link prediction or collaborative filtering problems in networks.The theoretical analysis of the above-mentioned algorithms requires advanced probabilistic tools. In particular, one of our proof is relying on a concentration inequality for U-statistics in a dependent framework. Few papers have addressed this thorny question and existing works consider sets of assumptions that do not meet our needs. Therefore, the second part of this manuscript will be devoted to the proof of a concentration inequality for U-statistics of order two for uniformly ergodic Markov chains. In Chapter 5, we exploit this concentration result for U-statistics to make new contributions to three very active areas of Statistics and Machine Learning.Still motivated by link prediction problems in graphs, we study post-selection inference procedures in the framework of logistic regression with $L^1$ penalty. We prove a central limit theorem under the distribution conditional on the selection event and derive asymptotically valid testing procedures and confidence intervals

Mestrado Vinifera EuroMaster - Instituto Superior de Agronomia
The characteristics of the berries and the seeds of two Sicilian cultivars compared to an international variety have been studied to gain a better understanding of some aspects concerning the reproductive process and fruit set in grapevine. Particularly, the empty-seededness phenomenon and its impact have been investigated by performing some viticultural practices in a randomized complete block in a wine grape vineyard located in the North-West Sicily, South Italy. This phenomenon led to empty seeds due to the embryo that aborts later becoming very small and endosperm that shrivel and degenerate, leaving them more or less hollow. It was evaluated how the performed treatments may affect these aspects evaluating their impact on the vegetative growth and productive activity. The leaf removal appeared suitable to prevent empty-seededness phenomenon decreasing floater seeds number in cultivars Grillo and Merlot, whereas in cv Nero D’Avola the tipping treatment was particularly relevant reducing the floater seed percentage

An investigation of austenite grain growth of two bearing steel grades; 100Cr6 and100CrMnMoSi8-4-6 is performed. Austenitization treatments were performed between 860°C and 1200 °C for 5 minutes to 5 hours and the grain size was determined for each sample.Grain boundary etching was carried out using a water based, picric-acid etchant. Generally,100CrMnMoSi8-4-6 was harder to etch than 100Cr6. Therefore, a precipitation heattreatment was performed in order to facilitate etching of prior austenite grain boundaries in100CrMnMoSi8-4-6. The precipitation treatment was found to be effective. However, theprecipitation heat treatment was not suitable for 100Cr6 as the grain size increased duringthe precipitation heat treatment.Light optical microscope equipped with a camera was utilized to take micrographs for grainsize evaluation. Jeffries' standard procedure according to ASTM E112-96 was used tomeasure the grain size. The results shows that the austenite grain size increases withtemperature and time as expected. The experimental data was fitted to a well-known graingrowth model. The model only worked for the temperatures investigated and could not bemade to fit different temperatures.Local grain size variation was studied and its influence on fatigue properties was evaluated.The result showed that variation in local grain size can significantly alter the fatigueproperties. The findings are only theoretical and have not been tested practically.Two different spheroidization heat treatments and one homogenization heat treatmentwere performed. Both spheroidization heat treatments investigated exhibited similar grainsize. The homogenization heat treatment reduced the local grain size variation.Homogenization treatment prior to the spheroidization treatments did not increase ordecrease the grain size. The long heating, holding and cooling times in the secondspheroidization heat treatment is probably the reason for the lack of grain refinementcompared to the first spheroidization heat treatment. The grains had time to grow to theinitial austenite grain size during each cycle.

The objective of this study is to develop crack growth analysis methods for functionally graded materials under mode I cyclic loading by using finite element technique. The study starts with the analysis of test specimens which are given in ASTM standard E399. The material properties of specimens are assumed to be changing along the thickness direction according to a presumed variation function used for the modeling of functionally graded materials. The results of the study reveal the influence of different material variation functions on the crack growth behavior. In the second part, the growth of an elliptical crack which is a common case in engineering applications is analyzed. First, mode I cycling loading is applied perpendicular to the crack plane and crack growth profiles for a certain number of cycles are obtained for homogeneous materials. Then, the code is extended for the analysis functionally graded materials. The material properties are assumed to vary as an exponential function along the major or minor axis direction of the crack. The results can be used to examine the crack profile and material constants&rsquo
influence for a certain number of cyclic loading.

Piecewise latent class growth analysis (LCGA) was used to examine growth patterns in reading comprehension and passage reading fluency on easyCBM, a popular formative assessment system. Unlike conventional growth modeling, LCGA takes into account the heterogeneity of growth and may provide reliable predictions for later development. Because current methods for classifying students are still questionable, this modeling technique could be a viable alternative classification method to identifying students at risk for reading difficulty. Results from this study suggested heterogeneity in reading development. The latent classes and growth trajectories from the LCGA models were found to align closely with easyCBM's risk rating system. However, results from one school district did not fully generalize across another. The implications for future research on examining growth in reading are discussed.

Thesis (MSc)--Stellenbosch University, 2015.
ENGLISH ABSTRACT: Grape quality is important for the producer, exporter and the consumer. Consumers judge table grapes according to their size, colour, taste and shelf life. The consumer’s prerequisites will influence the producer. Therefore, it is essential to know how the table grape berry develops so that it can be manipulated, favouring the postharvest quality and shelf life. This study was performed on Prime and Crimson Seedless, both grafted onto Ramsey, in the Paarl district of South Africa. The aim of this study was to describe and quantify table grape berry development and compositional changes taking place throughout growth and ripening. The effect of sugar:acid ratio on postharvest shelf life was also evaluated. To evaluate whether berry size influenced the measured development parameters, three berry sizes were induced for both cultivars by using plant bioregulators such as gibberellic acid (GA3) and forchlorfenuron – synthetic cytokinin (CPPU) or girdling. The following sizes were obtained for Prime: (i) small berries (<20 mm) with no treatment, which acted as the control; (ii) medium berries (20-24 mm) obtained by 15 ppm GA3 application at 8 mm berry size; (iii) large berries (>24 mm) obtained by combination of 15 ppm GA3 and 1 ppm CPPU application at 8 mm berry size. Crimson Seedless berry sizes were as follows: (i) small berries (<18 mm) with no treatment, which acted as the control; (ii) medium berries (18-22 mm) treated with 10 ppm GA3 at 7 mm berry size; (iii) large berries (>22 mm) treated with 10 ppm GA3 and vines were girdled at 7 mm berry size. To evaluate the effect of sugar:acid ratio on postharvest shelf life, grapes were stored for five weeks at -0.5 ˚C and another week at 7.5˚C. The bunches were evaluated for loose berries, browning, soft tissue breakdown, decay and berry split. The following components were analysed for both cultivars to determine changes in berry composition throughout the season: berry fresh weight, total soluble solids (TSS), glucose, fructose, titratable acidity (TA), tartaric acid, malic acid, abscisic acid (ABA) and total phenols. Total and individual anthocyanins were analysed for Crimson Seedless. Differences were obtained for the three berry sizes for both cultivars. Véraison, representing the start of ripening, started at the same time in successive seasons: 21 days after pea size berry (5 mm berry diameter) for Prime and 28 days after pea size berry (5 mm berry diameter) for Crimson Seedless. A lag stage was not observed, at seven day sampling intervals, for either of the cultivars. Components such as TSS, glucose, fructose and TA content per berry were influenced by berry size in either one or in both seasons for both cultivars. Significant changes in component concentration were detected at the start of, or around véraison. Sugar concentrations (TSS) already started to increase for both cultivars before the start of véraison. At véraison, concentrations of glucose, fructose and ABA increased while concentrations of TA, tartaric acid, malic acid and total phenols decreased. Total anthocyanins in Crimson Seedless started to increase one week after véraison commenced. The main anthocyanin found in Crimson Seedless was peonidin-3-glucoside. During ripening a 1:1 glucose:fructose ratio was detected in both cultivars. Prime tartaric:malic acid ratio was lower than Crimson Seedless tartaric:malic acid ratio in both seasons. Tartaric acid was the main organic acid found in Prime, while malic acid was the main organic acid found in Crimson Seedless. No significant differences were found in the postharvest defects between the different berry sizes. However, tendencies for differences were observed which led to the assumption that medium size berries were more prone to loose berries in both cultivars. Large berries showed a higher percentage berry split for both cultivars. Crimson Seedless second harvest date took place 24 hours after rainfall which could have very likely led to the higher percentages berry defects compared to the first season. Greater berry decay was found with later harvest dates for both cultivars. No significant differences were found for the TSS:TA ratio between the three berry sizes for both cultivars. Postharvest defects were therefore found not only to be influenced by TSS:TA ratio but rather by harvest date and packing procedures. Environmental conditions prior to harvest also had an impact on postharvest shelf life.
AFRIKAANSE OPSOMMING: Druif kwaliteit is belangrik vir die produsent, uitvoerder en verbruiker. Tafeldruiwe word gekeur deur die verbruiker volgens grootte, kleur, smaak en raklewe. Die verbruiker se voorkeure sal dus die produsent beïnvloed. Daarom is dit belangrik om te weet hoe tafeldruiwe ontwikkel ten einde korrelsamestelling te manipuleer om na-oes kwaliteit en raklewe te kan bevoordeel. Hierdie studie is uitgevoer op Prime en Crimson Seedless, beide geënt op Ramsey, in die Paarl distrik van Suid Afrika. Die doel van die studie is om vas te stel hoe korrelsamestelling gedurende groei en rypwording verander. Die effek van suiker:suurverhouding op na-oes raklewe is ook geëvalueer. Om te kan meet of korrel grootte die gemete parameter beïnvloed is drie korrelgroottes verkry vir albei kultivars deur die gebruik van plant bioreguleerders, te wete gibbereliensuur (GA3) en sintetiese sitokiniene (CPPU), of ringelering. Die volgende korrelgroottes is verkry vir Prime: (i) klein korrels (<20 mm) d.m.v. geen behandeling, geklassifiseerd as kontrole; (ii) medium korrels (20-24 mm) d.m.v. ‘n 15 dpm GA3 behandeling by 8 mm korrelgrootte; (iii) groot korrels (>24 mm) d.m.v. ‘n kombinasie van 15 dpm GA3 en 1 dpm CPPU by 8 mm korrelgrootte. Crimson Seedless korrelgroottes was soos volg: (i) klein korrels (<18 mm) d.m.v. geen behandeling, wat as kontrole gedien het; (ii) medium korrels (18-22 mm) d.m.v. ‘n 10 dpm GA3 behandeling by 7 mm korrelgrootte; (iii) groot korrels (>22 mm) d.m.v. ‘n 10 dpm GA3 behandeling en gelyktydige ringelering by 7 mm korrelgrootte. Om die effek van suiker:suur verhouding op na-oes houvermoë te kon evalueer was druiwe gestoor vir vyf weke by -0.5˚C en ‘n verdere week by 7˚C. Die trosse is geëvalueer vir loskorrels, verbruining, sagte weefsel afbreek, verval en korrelbars. Die volgende komponente is geanaliseer vir albei kultivars om veranderinge in korrelsamestelling gedurende die seisoen te bepaal: vars korrelgewig, totale oplosbare vaste stowwe (suikerinhoud), glukose, fruktose, titreerbare sure, wynsteensuur, appelsuur, absisiensuur en totale fenole. Die totale en individuele antosianiene is ook vir Crimson Seedless gemeet. Beduidende verskille tussen die drie korrelgroottes vir albei kultivars is verkry. Deurslaan, naamlik die begin van rypwording, het op dieselfde dag in opeenvolgende seisoene plaasgevind: 21 dae na ertjiekorrel grootte (5 mm korrel deursnee) vir Prime en 28 dae na ertjiekorrel grootte (5 mm korrel deursnee) vir Crimson Seedless. In teenstelling met die tipiese korrel ontwikkelingspatroon is ‘n rusfase nie waargeneem by beide kultivars nie. Komponente soos suikerinhoud, glukose, fruktose en titreerbare suur inhoud per korrel is deur korrelgrootte beïnvloed in een of albei seisoene vir beide kultivars. Suiker konsentrasie van albei kultivars het reeds voor deurslaan begin toeneem. By deurslaan het die konsentrasies van glukose, fruktose en absisiensuur inhoud toegeneem, terwyl die konsentraies van titreerbare sure, wynsteensuur, appelsuur en totale fenole gedaal het. Totale antosianiene in Crimson Seedless het ‘n week na deurslaan begin toeneem. Die hoof antosianien in Crimson Seedless is peonidien-3-glukosied. Gedurende rypwording was daar ‘n 1:1 glukose:fruktose verhouding gevind vir beide kultivars. In terme van sure is Prime se wynsteensuur:appelsuur verhouding laer as in Crimson Seedless vir albei seisoene. Wynsteensuur is die hoof organiese suur in Prime terwyl appelsuur die hoof organiese suur in Crimson Seedless is. Geen betekenisvolle verskille vir na-oes houvermoë tussen korrelgroottes is waargeneem vir beide kultivars nie. Daar was egter tendense wat aanleiding gegee het in die aanname dat medium grootte korrels geneig is tot loskorrels in albei kultivars. Groot korrels het ‘n hoër korrelbars persentasie getoon vir beide kultivars. Crimson Seedless se tweede oes het plaasgevind 24 uur na reënval, wat aanleiding gegee het tot hoër persentasies korrelbederf. Hoër persentasie korrelbederf was ook gevind met later oesdatums. Geen beduidende verskille is gevind vir suiker:suur verhouding tussen die drie korrelgroottes vir beide kultivars nie. Dus word na-oes houvermoë nie net deur suiker:suur verhouding beïnvloed nie, maar ook deur oestyd en verpakkingsprodsedures. Omgewingsomstandighede voor oes kan ook na-oes houvermoë beïnvloed.

There is ongoing debate among researchers and educators regarding the utility of English L1 practices for English-as-an-Additional-Language (EAL) learners who are in need of special education services. The identification of reading disability for EAL children is often delayed because relatively little is known about how EAL learners develop to be competent readers. This study sought to address this by providing descriptions of how children grow in their literacy skills and what predicts successful acquisition of these skills. This longitudinal study followed 773 L1 and 182 EAL children from grades 2 through 7. Multi-group latent growth analyses provided compelling evidence for common developmental models for L1 and EAL in word recognition, word reading fluency, decoding, decoding fluency, reading comprehension, and spelling. Phonological processing, syntactic awareness, and verbal working memory were important predictors of growth for children from both language groups. Growth models also show that poor readers from both language groups continued to be behind normally achieving peers. For poor readers, growth in word recognition, word reading fluency, decoding, decoding fluency, and reading comprehension was characterized by a persistent deficit model. In contrast, there was a cumulative deficit for spelling. That is, poor readers started out with poor spelling skills and progressed at a slower rate than normally achieving readers, thus widening the gap over time. Poor readers, as a group, also demonstrated weaknesses across phonological processing, syntactic awareness, and verbal working memory. Overall, the results of this study highlight the importance of early services and assessment for all children at risk for reading disability, regardless of first language status.

Jusqu'à récemment, les variétés destinées à la production de vin (majoritairement V. vinifera) ont été sélectionnées pour forte accumulation en sucres et composés du métabolisme secondaire (arômes, tanins, anthocyanes). Certains paramètres du changement climatique (températures, CO2) accentuent la tendance à l'augmentation des teneurs en sucres à la récolte donnant des vins plus alcooleux. L'augmentation de la teneur en alcool des vins est un phénomène planétaire, avec des augmentations annuelles de 0,16%. Cela altérant le profil qualitatif notamment en impactant l'équilibre alcool/acidité et pose un problème vis-à-vis de la santé des consommateurs.Le raisin est un fruit pulpeux non-climactérique se développant en deux phases. La première est la phase herbacée durant laquelle s’accumule majoritairement les acides maliques et tartriques. Durant cette phase, la baie grossit par mitose et expansion vacuolaire. La deuxième phase de croissance est associée à l'importation massive d'hexoses, d’eau et de potassium. A la fin de la deuxième phase de croissance, le phloème arrête son déchargement et la baie concentre ses principaux métabolites par évaporation. Certaines pratiques œnologiques permettent de réduire les teneurs en sucres des moûts ou en alcool des vins (CEE-606/2009 et CEE-53/2011), mais sont partielles ou coûteuses et peuvent impacter la qualité des vins. Les pratiques culturales ne modifient pas suffisamment le développement du raisin pour être efficaces, sauf à dégrader le potentiel qualitatif de la vendange. Sur le long terme, l'approche la plus prometteuse est la sélection variétale.Ce dernier aspect fut abordé dans le projet de thèse. En premier lieu, de nouvelles stratégies/outils de phénotypage permettant la caractérisation du développement du raisin furent développés. Ensuite, la diversité pour l'accumulation des métabolites primaires dans le raisin (V. vinifera) ou pouvant être généré par croisement avec la microvigne fut analysée. Dans un dernier volet, la caractérisation physiologique de génotypes issus d’un croisement entre V. vinifera et M. rotundifolia présentant un caractère de faible accumulation en sucres durant la maturation des raisins fut approfondie.Les résultats principaux de ce travail indiquent :1) Il est possible d’apprécier le développement d'une population de baies tant en asynchronie (bains densimétriques) qu’en hétérogénéité (Dyostem). La couleur du fruit n’était pas un bon indicateur du début de la maturation, apparaissant 1 à 5 jours après les premier signes de ramollissement des baies. Par ailleurs, les suivis réalisés à l'échelle de population de baies ont montré que pour des analyses fines, il était préférable d’analyser le fruit unique.2) Il existe une grande diversité chez V. vinifera pour ce qui concerne la compositions en métabolites primaires des baies et leurs dilutions. La possibilité de ségréger indépendamment l'accumulation d'eau, des sucres, des acides et des cations fut révélée, ouvrant d’intéressantes perspectives en termes d'innovation variétale.3) L’analyse du caractère faible teneur en sucres chez des descendants de V. vinifera et M. rotundifolia montre que ce caractère ne résulte ni d’une limitation ou d'un décalage de l'accumulation, ni d’une plus grande hétérogénéité/asynchronie des baies. Les résultats suggèrent qu'il existe des différences mécanistiques entre niveau de croissance et pression osmotique du fruit lors de la maturation entre génotypes. Cette découverte soulève de nombreuses questions : existe-t-il des différences dans les structures des parois cellulaires ou de leurs enzymes associées ? Est-ce que les cellules des baies des génotypes à faible teneur en sucres sont plus grosses ou plus nombreuses que les variétés traditionnelles ?Deux de ces descendants ont été croisés avec la microvigne pour détecter les QTLs associés à ce caractère dans l'objectif d'identifier les fonctions contrôlant ce trait d'intérêt agronomique
Until recently, varieties used for wine production (mainly V. vinifera) have been selected for high sugar accumulation and secondary metabolism compounds (aromas, tannins, anthocyanins). Some climate change parameters (temperatures, CO2) accentuate the trend towards higher sugar levels at harvest, resulting in more alcoholic wines. The increase in wine alcohol content is a global phenomenon, with annual increases of 0.16%. This alters the qualitative profile, in particular by impacting the alcohol/acidity balance and poses a problem for consumer health.The grape is a non-climacteric fleshy fruit that develops in two phases. The first is the herbaceous phase during which malic and tartaric acids accumulate mainly accumulate. During this phase, the berry grows by mitosis and vacuolar expansion. The second phase of growth is associated with the massive import of hexoses, water and potassium. At the end of the second growth phase, the phloem stops unloading and the berry concentrates its main metabolites by evaporation. Some oenological practices make it possible to reduce the sugar content of must or alcohol wines content (CEE-606/2009 and CEE-53/2011), but are partial or costly and can have an impact on the wines quality. Cultivation practices do not sufficiently modify the development of the grape to be effective, except that they degrade the quality potential of the harvest. In the long term, the most promising approach is the variety selection.The latter aspect was addressed in the thesis project. First, new phenotyping strategies/tools were developed to characterize grape development. Then, the diversity for the accumulation of primary metabolites in grapes (V. vinifera) or that can be generated by crossing with the microvine was analysed. In the last part, the physiological characterisation of genotypes resulting from a cross between V. vinifera and M. rotundifolia with a low sugar accumulation character during grape ripening was further developed.The main results of this work indicate:1) It is possible to assess the development of a berries population both in asynchrony (densimetric baths) and in heterogeneity (Dyostem). The colour of the fruit was not a good indicator of the beginning of ripening, appearing 1 to 5 days after the first signs of berry softening. In addition, monitoring at the berry population level has shown that for fine analyses, it is preferable to analyse the single fruit.2) There is a great diversity in V. vinifera with regard to the composition of primary berry metabolites and their dilutions. The possibility of independently segregating the accumulation of water, sugars, acids and cations was revealed, opening up interesting prospects for varietal innovation.3) Analysis of the low sugar concentration trait in descendants of V. vinifera and M. rotundifolia shows that this characteristic does not result from a limitation or delay in accumulation or from greater heterogeneity/asynchrony of the berries. The results suggest that there are mechanistic differences between growth level and osmotic pressure of the fruit during maturation between genotypes. This discovery raises many questions: are there differences in the cell wall structures or their associated enzymes? Are berry cells of low sugar genotypes larger or more numerous than traditional varieties?Two of these descendants were crossed with the microvine to detect the associated QTLs to this trait in order to identify the functions controlling this agronomic interest trait

Doctor of Philosophy
Curriculum and Instruction Programs
Sherri Martinie
This study examined the impact grading policies have on students’ mindsets in urban Midwestern middle schools. The components of this quasi-experimental, causal comparative survey research relied on the grading policies in place at the school level and the students’ reporting of their mindset. Data was collected using a questionnaire containing eight Likert-type questions from the Implicit Theories of Intelligence scale (Dweck, 2006), as well as additional questions seeking the students’ perceptions of grading practices implemented in their buildings. Descriptive statistics, frequencies, t-tests and ANOVA tests were run measuring the impact that a variety of perceived grading practices had on students’ mindset levels. The findings from the research demonstrated no statistically significant differences between the mindset levels of students from schools with different grading policies. Further analysis revealed inconsistencies between student perceptions of the grading practices and the schools’ actual stated grading policies. It appears standards based and traditional grading practices, although specifically stated at the building level, appear to have blended together in the large school district, which may have led to the inconclusive results. Of significance was the finding that students perceived to understand the meaning of their grade, even if it is misaligned with the schools’ policy, reported a growth mindset in comparison to students that reported they did not understand their grade. These findings begin to explore the impact grading practices have on students, especially during the transition from traditional to standards based grading. Further research is needed to fully examine the transition between grading practices and students’ perceptions of those policies. When students’ perceptions of the standards based grading policy do not align with the actual policy, it is assumed that it will have no impact on students’ mindset levels. Future research would seek to understand ways in which educators making a transition from traditional to standards based grading can seek clarity of policies, seek accuracy of implementation and monitor students’ perceptions in alignment with the policies and practices.

Prohexadione-calcium (P-ca), as ApogeeTM, was evaluated in 2000 and 2001 for impact to grape vegetative and reproductive development. In 2000, P-ca (250 mg/L) was applied to Seyval, Cabernet Sauvignon, and Cabernet franc (125, 250, and 375 mg/L). P-ca reduced primary shoot growth for all cultivars and decreased cane pruning weight of Seyval. P-ca (375 mg/L) increased Cabernet franc canopy gaps but increased Cabernet Sauvignon lateral leaf area and leaf layer number. P-ca reduced components of yield for all cultivars. In 2001, P-ca (250 mg/L) was applied singularly at weekly intervals to Cabernet Sauvignon clusters and pre and post-bloom to Cabernet franc and Chardonnay canopies. Application at E-L stages 21 and 23 decreased Cabernet Sauvignon fruit set whereas application at E-L stages 26, 27, and 29 reduced berry weight without impacting fruit set. Berry weight reduction correlated to higher color intensity (420+520 nm), anthocyanins, total phenols and phenol-free glycosyl-glucose (PFGG). Cabernet franc vegetative and reproductive development was generally not affected yet treatment increased absorbance at 280, 420, and 520 nm, color intensity, anthocyanins and total phenols. Pre-bloom applications inhibited Chardonnay vegetative development, and reduced components of yield, and fruit chemistry values: hydroxycinnamates, total phenols, flavonoids, PPFG and absorbance at 280 and 320 nm. Post-bloom applications did not affect Chardonnay vegetative or reproductive development, yet increased PFGG. Treatment did not affect Chardonnay wine chemistry but two post-bloom applications increased Cabernet franc wine anthocyanins and total phenols. Wine aroma and flavor triangle difference tests did not indicate significant treatment differences.
Master of Science

Prolonged exposure to high ambient temperature without cooling causes heat stress (HS) resulting in altered growth, body composition and metabolic dysfunction in pigs. Grape seed extract (GSE) has been shown to reduce inflammation, and improve glucose transport and metabolism. Thus, GSE may be an effective supplement to combat the consequences of heat stress; however this possibility has not been evaluated in a large animal model. The objective of the current study was to examine the effect of GSE supplementation on pig performance and body composition during HS. Twenty-four female pigs (62.3± 8 kg BW) were randomly assigned to a 2X2 factorial experiment; thermal neutral (TN; 21-22°C) or heat stress conditions (HS; 33-34°C) for 7 days and fed either a control or a GSE supplemented diet (12mg/kg body weight). Body temperature (TB), respiration rate (RR) and feed intake (FI) were measured daily. Body composition was measured by dual-energy X-ray absorptiometry (DXA). Respiration rate and TB increased in the HS control group compared to the TN control group (p<0.05), however GSE did not alter these parameters compared to control for the duration of the 7 day period. HS decreased FI (P < 0.05). Fasting blood glucose concentrations were approximately 1.5-fold greater in the control diet compared to their GSE supplemented counterpart (p=0.067) on day 6 of the HS period, but did not differ between groups at the end of day 7 of HS. Body composition analysis indicated bone mineral density, bone mineral content, and percent change of fat remain unchanged between treatment groups. Percent change in weight was significantly reduced in HS. Lean tissue accretion was 45% greater in TN compared to HS groups (p<0.05). Endotoxin concentrations were approximately 2-fold lower in the HS-GSE group compared to the control (P=0.083). Grape seed extract supplementation does not appear to alter pig growth performance or body composition, but does appear to delay the onset of reduced feed intake by 1 day, reduce intestinal permeability, and improve insulin sensitivity during additional stress.
Master of Science in Life Sciences

Efforts to understand growth and disparities in science achievement have mainly been focused on the middle and high school grades in studies of K – 12 science education, leaving a gap in the research about the early elementary years. This study used a nationally-representative sample of students in Grades K – 2 to examine science achievement and growth trajectories of students by gender and race/ethnicity. Using multilevel growth modeling, differences in science achievement at Grade 2 and in rate of growth were detected for several student groups. Socioeconomic status, prior reading and math achievement, and student home language status were also significant predictors of science achievement. Growth effect size estimates were calculated by student group and showed substantial year-to-year growth in science achievement in the early elementary grades, with a slight decrease in effect size across years. In order to strengthen current efforts to increase student engagement and participation in science and STEM-related career and college pathways, especially for historically underrepresented groups, policymakers should shift focus to better understand promising practices that best support all students in science from the onset of their K – 12 educational experience.

Mestrado Vinifera EuroMaster - Instituto Superior de Agronomia
A study to compare the effects of hedging and curling the shoot tips (rolling) on the last wire of the trellising system was carried out in Saint Emilion (France) on Merlot grapevines in 2011. Vines were hedged or curled when shoots were 30 – 40 cm longer than the highest wire. The effects of the two canopy management strategies on vine performance, mainly vegetative growth, disease occurrence, phenology, water status, yield components and berry composition were compared. Curled, not hedged vines presented longer main shoots, more lateral shoots and higher potassium values on the petioles. Hedged plants had a higher percentage of shaded clusters and a higher leaf layer number at the cluster zone and ¾ of the canopy. Regarding leaf area, curled plants presented a bigger main leaf area but for lateral leaf area no differences were found. Although berries on hedged plants were prone to have a higher mass, no differences for berry composition were found. Hedging seems to be an appropriated technique for the Sain Emilion region as it is less time consuming, less expensive, possible to be mechanized and it has no detriment regarding quality of berries

The purpose of this study was to examine the relationship between English language proficiency scores as measured by the ACCESS for ELLs and achievement and growth scores on the reading subtest of the Measures of Academic Progress (MAP). The sample consisted of 2,006 3rd-5th grade English language learners (ELLs) from a large Midwestern school district. Results confirmed that an increase in English proficiency is associated with higher reading achievement scores. The unique variance explained by each of the domain scores (reading, writing, speaking, and listening) on the ACCESS for ELLs supports the use of a weighted composite score for decision making purposes. When considering within-year MAP growth by differing levels of proficiency, a curvilinear trend emerged. The two lowest proficiency groups demonstrated significantly lower reading growth than the two moderate and two highest proficiency groups. The greatest growth was seen by the two groups in the middle of the proficiency spectrum. Given the increased demands on measuring the achievement and progress of all students, including ELLs, and the use of standardized achievement scores for program and teacher evaluation, the results of this study suggest that a dichotomous classification of ELL/non-ELL might not accurately reflect the variability in growth at various levels of English proficiency. Implications for interpreting and using scores by ELLs are discussed.

Growth of terrace graded virtual substrates, pioneered by Capewell (2002), has been conducted utilising solid-source molecular beam epitaxy (SS-MBE) to produce structures of higher germanium composition (up to pure germanium) and greater thickness (up to 20 ?m) than previously investigated. Terrace grading offers a number of advantages over more conventional grading techniques which include the reduction of surface threading dislocation density, reduction of surface roughness and the possibility of the complete elimination of threading dislocation pile-up. The closely spaced pile-up of threading dislocations is believed to have a significant impact on the electrical properties of processed devices, and its elimination is a key goal in this work. Numerous terrace graded virtual substrate compositions have been grown and characterised during the course of this work and, where appropriate, comparison made with more conventional structures. The complete elimination of threading dislocation pile-up has been demonstrated at compositions of 30% and 40%, with a reduced threading dislocation density in comparison to equivalent liner graded structures. A major reduction in threading dislocation density has been accomplished though post growth ex-situ annealing at 900?c for an extend period of time, though the exact mechanism remains uncertain. The possible role of surface precipitates enabling reduction of dislocation pile-up and/or density is considered along with the effects of unwanted particulate contamination during growth.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1998.
Includes bibliographical references (leaves 137-147).
Silicon germanium layers on silicon substrates (SiGe/Si) are useful for a variety of microelectronics applications. The most successful technique for growing low defect density relaxed SiGe/Si layers is relaxed compositional grading. However, with increasing Ge content in the graded SiGe layers, the following materials concerns need to be addressed-{i) a high surface roughness, (ii) the formation of dislocation pile-ups, (iii) an increase in the threading dislocation density, (iv) tensile strains and micro-cracking due to thermal mismatch, and (v) particulate contamination from germane gas phase nucleation. We have grown relaxed graded SiGe/Si layers using ultra-high vacuum chemical vapor deposition (UHVCVD) at growth temperatures ranging between 500°-900° C and pressures between 30-500 millitorr. The SiGe growth rates at different temperature and Ge content regimes agree with previously proposed theories. By applying both a dislocation blocking criterion and surface roughness effects to graded SiGe/Si structures, we have proposed a model to explain and predict the formation of dislocation pile-ups in graded structures. We have discovered that there is a substantial improvement in the surface roughness and dislocation pile-up density in graded SiGe layers by growing on miscut Si(00l) substrates. It was found that the array of 60° dislocations that usually forms to relieve the misfit stress could transform into a novel lower energy hexagonal dislocation network consisting of all edge dislocations. High resolution X-ray diffraction measurements indicate that there is a decrease in the rate of epilayer tilting in the Ge-rich layers of the graded buffer in agreement with the observed dislocation structure. We have designed an optimized relaxed buffer (ORB) process that allows us to grow high quality Ge layers on Si substrates. By employing a chemical mechanical polishing (CMP) and regrowth step within the epitaxial structure, we have minimized the formation of dislocation pile-ups. Compressive strain has been incorporated into the graded layers to overcome the thermal mismatch problem. The ORB process eliminates dislocation pile-ups, decreases gas-phase nucleation of particles, and eliminates the increase in threading dislocation density. Germanium p-n photodiodes were fabricated to assess the diectronic quality and prove the feasibility of a high quality infrared detector on a Si substrate. The dark current in the diodes was at least two orders of magnitude lower than any previously reported value for Ge photodiodes on Si substrates. Capacitance measurements indicate that the devices are capable of high speed operation. Dislocation filtering experiments were conducted to reduce threading dislocation densities on pattered mesas. It was found that at the strain levels from small compressive mismatch, dislocation nucleation from the mesa edges dominates over dislocation filtering.
by Srikanth B. Samavedam.
Ph.D.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
O Brasil possui vantagens competitivas que, no caso da uva, se resumem na possibilidade de produção e exportação da fruta durante alguns meses, quase sem concorrência. Porém, alguns fatores têm limitado a expansão do cultivo para áreas tropicais, como por exemplo, a baixa produtividade de cultivares pouco adaptados. Assim, este projeto de pesquisa teve por objetivo estudar o efeito da aplicação de novos produtos visando uniformizar a brotação e aumentar a produtividade e a qualidade de bagas do cultivar de uva sem sementes Superior Seedless. Os experimentos foram conduzidos na Fazenda Koshiyama, localizada no município de Juazeiro/BA, no período de 15/05 a 21/09/2006. Com a finalidade de avaliar o efeito do biorregulador Stimulate® (0,009% de cinetina (citocinina), 0,005% de ácido giberélico (GA3), 0,005% de ácido indolilbutírico (IBA-auxina) e 99,981% de ingredientes inertes) e de X-Cyte® (0,04% de cinetina (citocinina) e 99,96% de ingredientes inertes) na uniformidade de brotação e dos biorreguladores Stimulate®, X-Cyte® e N-Large® (4% de ácido giberélico (GA3) e 96% de ingredientes inertes) no desenvolvimento das bagas, foram conduzidos três experimentos. Experimento 1: T1: Dormex® (5%); T2: Dormex® (5%) + Nitro Plus 9®; T3: Stimulate® (0,5%); T4: Stimulate® (0,5%) + Nitro Plus 9®; T5:Stimulate® (1,0%); T6: Stimulate® (1,0%) + Nitro Plus 9®; T7: X-Cyte® (0,25%); T8: XCyte ® (0,25%) + Nitro Plus 9®; T9: X-Cyte® (0,50%); T10: X-Cyte® (0,50%) + Nitro Plus 9®; T11: X-Cyte® (0,25%) + Stimulate® (0,5%) e; T12: X-Cyte® (0,25%) + Stimulate® (0,5%) + Nitro Plus 9®. Experimento 2: T1: Pro-Gibb®; T2: Stimulate® (Dose 1); T3: Stimulate® (Dose 2); T4: Stimulate® (Dose 3); T5: Pro-Gibb® + X-Cyte® (Dose Baixa - DB); T6: Pro-Gibb® + X-Cyte® (Dose Média - DM); T7: Pro-Gibb® + X-Cyte®...
Brazil has some competitive advantages in grape production, specially harvesting all-year-around in almost the whole of the country. Therefore, Brazilian fruits can be exported for a few months practically without international competition. However, some factors have been limiting grape growing expansion in tropical areas. For example, low yields of less adapted cultivars. The field trials of this work were performed between May 15th and September 21st 2006, at Koshiyama farm, in Juazeiro municipality (Bahia State / Northeastern Brazil). The main goal was to analyze the effect of new commercial products intended to uniformizar sprouting, increasing yields and berry quality for Superior Seedless grapes. It was evaluated the effect of the following bioregulators in sprouting uniformity: Stimulate® (0,009% de kinetin (cytokinin), 0,005% of gibberellic acid (GA3), 0,005% indolbutiric acid (IBA-auxin); 99,981% of inert ingredients); X-Cyte® (0,04% kinetin (cytokinin) and 99,96% of inert ingredients). Three field trials were also performed, to verify the effect of Stimulate®, X-Cyte® e N-Large® (4% gibberellic acid (GA3) and 96% inert ingredients) on berry development: Trial 1: T1: Dormex® (5%); T2: Dormex® (5%) + Nitro Plus 9®; T3: Stimulate® (0,5%); T4: Stimulate® (0,5%) + Nitro Plus 9®; T5: Stimulate® (1,0%); T6: Stimulate® (1,0%)+ Nitro Plus 9®; T7: X-Cyte® (0,25%); T8: X-Cyte® (0,25%) + Nitro Plus 9®; T9: X-Cyte® (0,50%); T10: X-Cyte® (0,50%) + Nitro Plus 9®; T11: X-Cyte® (0,25%) + Stimulate® (0,5%)e; T12: X-Cyte® (0,25%) + Stimulate® (0,5%) + Nitro Plus 9®. Trial 2: T1: Pro-Gibb®; T2: Stimulate® (Dose 1); T3: Stimulate® (Dose 2); T4: Stimulate® (Dose 3); T5: Pro-Gibb® + XCyte ® (Low Dose - DB); T6: Pro-Gibb® + X-Cyte® (Intermediate Dose- DM); T7: Pro-Gibb® + X-Cyte® (High Dose- DA); T8: N-Large®; T9: N-Large® + X-Cyte® (DB); T10: N-Large®... (Complete abstract click electronic access below)

Grafts currently used for the repair of anterior cruciate ligament (ACL) ruptures integrate poorly with bone due to a significant mismatch in properties between graft and bone. Specifically, conventional grafts (e.g., hamstring tendon) are unable to recapitulate intricate gradients in mechano-chemical properties and extracellular matrix (ECM) architecture found at natural bone-ligament (B-L) transitions, and thus result in stress-concentrations at the graft-bone interface leading to graft failure. In contrast, tissue-engineered scaffolds possessing gradients in properties can potentially guide the establishment of phenotypic gradients in bone marrow stromal cells (BMSCs), and thus aid the regeneration of B-L transitions in the long-term. Towards the eventual goal of regenerating complex tissue transitions, this project employs three complementary strategies to fabricate graded scaffolds. The three strategies involve the presentation of gradients in 1) mineral content, 2) scaffold architecture and 3) growth factor (GF) concentration within scaffolds to control BMSC morphology and phenotype.

The first strategy involved co-electrospinning two polymers (one doped with hydroxyapatite) from offset spinnerets onto a rotating drum to produce scaffolds possessing a gradient in mineral content. Post-electrospinning, these graded scaffolds were treated with a simulated body fluid to further enhance the gradient. Analysis of mRNA expression of osteoblastic makers by BMSCs and the deposition of bone-specific ECM proteins indicated that the scaffolds could guide the formation of an osteoblastic phenotypic gradient. The second strategy involved electrospinning two polymer solutions onto a custom-designed dual-drum collector to fabricate scaffolds possessing region-wise differences in fiber alignment, diameter and chemistry. Specifically, electrospinning onto the dual-drum collector resulted in the deposition of aligned fibers from one polymer solution in the gap region between the drums, randomly oriented fibers from the other polymer solution on one of the drums and a mixture of fibers from both polymer solutions in the overlap region in between. The topographical cues within these scaffolds were shown to result in region-dependent BMSC morphology and orientation. Although the long-term goal of the third strategy was to create a co-electrospun scaffold possessing a gradient in GF concentration, a new technique to protect GF activity within electrospun scaffolds via the use of gelatin microspheres was first validated. Preliminary results from these studies indicate that microspheres can protect and deliver a model protein (lysozyme) in active conformation from electrospun scaffolds. These results further suggest that gradients of GF concentration can be achieved in the long-term by protecting GFs within microspheres and co-electrospinning as described in the first strategy.

In conclusion, the results from this project suggest that graded scaffolds can help guide the formation of gradients in cell morphology, orientation and phenotype, and thus potentially promote the regeneration of B-L transitions in the long-term. The three strategies described in this project can be employed in concert to create scaffolds intended for the regeneration of complex tissue transitions.
Ph. D.