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1
Henshaw, Alex. "Factors Influencing Future Canopy Composition at Tiromoana Bush, North Canterbury, New Zealand". Thesis, University of Canterbury. School of Forestry, 2012. http://hdl.handle.net/10092/7092.
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The purpose of this study was to investigate seedling recruitment beneath kanuka forest at Tiromoana Bush, North Canterbury. The regeneration of broadleaved tree species is evident throughout Tiromoana Bush. This research aimed to quantify the biotic and abiotic factors influencing the distribution of small and large seedlings of canopy tree species, their relative growth rates, their survival, abundance and composition throughout the forest understorey of Tiromoana Bush. Tiromoana Bush is a forest restoration area of 410 hectares adjacent to the Kate Valley landfill.
To determine the future tree species composition at Tiromoana Bush, seedling recruitment, growth and survival was quantified through remeasuring tagged seedlings in 26 permanent vegetation monitoring plots located in the major forest patches at Tiromoana Bush. In addition, seedling data from 78 temporary vegetation survey plots established in three major forest patches were used to assess the influence of different factors on seedling abundance.
At Tiromoana Bush, the most common canopy tree species as seedlings in the permanent vegetation monitoring plots was mahoe followed by fivefinger. Mahoe seedling density was significantly affected by canopy openness, distance to seed sources, light index, shrub cover and slope, but not by aspect, basal area and time. For fivefinger, seedlings increased in abundance with time, but the difference was not statistically significant. The relative growth rate of mahoe in the 20-49cm height class (in which most seedlings occurred) was significantly affected by shrub cover, light index and canopy
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openness. Mahoe seedling recruits were significantly affected by light index and canopy openness. Survivability of mahoe was affected by aspect. For fivefinger, individual relative growth rates were significantly affected by canopy openness and light index.
Similar results were found for tree species seedlings present in the temporary survey plots provided with mahoe and fivefinger again the most common species, followed by kohuhu. Light index significantly affected golden akeake small seedlings as well as canopy openness. Light index significantly affected ngaio large seedling distribution. Aspect was the only significant factor for kohuhu large seedling distribution. Distance from seed sources significantly affected fivefinger small seedling distribution as seedlings are dependent upon dispersal away from the parent trees. Slope significantly affected the distribution of red matipou small seedlings.
The most important environmental attribute influencing seedling abundance is light. This is evident in both the permanent seedling monitoring plots and the temporary vegetation survey plots. Based on data from the temporary vegetation survey plots, mahoe, fivefinger and kohuhu are most abundant suggesting that these three canopy tree species will dominate the forest canopy at Tiromoana Bush once the kanuka starts to senesce.
2
Reffruschinni, Katie, David Robinson i Albert Dobrenz. "Seedling Alfalfa Root Research". College of Agriculture, University of Arizona (Tucson, AZ), 1987. http://hdl.handle.net/10150/203792.
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There has been limited research on the rooting patterns of alfalfa. This information would be important in developing new germplasm sources that are more water efficient, salt tolerant and drought tolerant. Ten alfalfa varieties were evaluated for possible genetic control of rooting traits. Seedlings were grown hydroponically in a growth chamber. The cultivars evaluated showed a significant statistical difference for width of lateral root system and number of lateral roots. The variation in seedling rooting patterns is sufficient to warrant a selection program for improved lateral rooting patterns.
3
Telewski, Frank W. "The Impact of Ozone on Sequoia Seedling Stem Structure: Implications for Seedling Survival". Laboratory of Tree-Ring Research, University of Arizona (Tucson, AZ), 2013. http://hdl.handle.net/10150/302708.
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Agyeman, Victor Kwame. "Environmental influences on seedling growth". Thesis, University of Aberdeen, 1994. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU068823.
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The tropical high forests of West Africa have been under stress due to a greater dependence on wood resources. Logging rate has more than doubled within the last decade. However, the exact effects of logging on vegetation composition and the degree of canopy opening that should be created in the forest to ensure the regeneration of timber tree species are not known. Three major experiments were carried out to determine the ecophysiological responses of timber tree species in different irradiances and red:far-red ratios. (1) 16 tree species were grown in six neutral shade treatments (2, 6, 27, 42 and 65% full sun) and their growth assessed by standard measurements used in growth analysis (biomass, height, stem diameter, leaf area, leaf production and mortality). (2) Eight species, of which six were also used in the shade house experiment, were grown in a series of artificially-created gaps in two forest sites differing in annual rainfall. Gaps created received 1-2, 5, 10, 15, 30 and 66% full sun. (3) Possible differences in the results between shade house and forest experiments due to differences in light quality (red:far-red ratio) were tested separately. Differences in red:far-red ratio has little effect of growth but showed some influence on allocation of biomass. Seedling growth response of species were higher in shade houses compared to the two field sites and higher in the wet compared to dry forests. Sixteen tropical timber tree species were ranked on an ecological (shade tolerance) gradient based on their differential growth response to light. The results indicate that the ranking of species on an ecological gradient is robust and potentially more reliable than intuitive classification of species into groups.
5
Hunt, Jeff K. Hung John Y. McDonald Timothy P. "Pine seedling detection and registration". Auburn, Ala., 2009. http://hdl.handle.net/10415/1959.
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Kamboozia, Jafar. "Seedling vigour in winter grain legumes". Title page, table of contents and abstract only, 1994. http://web4.library.adelaide.edu.au/theses/09PH/09phk152.pdf.
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Kappala, Saritha. "Seedling establishment on Oryza sativa L". Thesis, University of Liverpool, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.540049.
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Nielsen, Michele Erin. "Seed and seedling dynamics of the seagrass, Zostera japonica Aschers. and Graebn. and the influence of Zostera marina L". Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/30172.
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The seagrass Zostera japonica Aschers. and Graebn. occurs as pure populations and in mixture with Zostera marina L. along the intertidal regions of southwest British Columbia. At the Roberts Bank study area seed and seedling dynamics were studied in three vegetation zones: a landward monospecific zone of Z. japonica, a zone of co-existing Z. japonica and Z. marina, and a seaward monospecific zone of Z. marina. Many more seeds were produced than were found in the sediment, and even fewer germinated. Zostera japonica seeds were most abundant in the seed bank in the upper zones where there is high Z. japonica density. Even though seeds remained in the water column for up to two months, very few seeds dispersed into the lower zone populated by Z. marina. thus limiting Z. japonica's colonization of the lower zones. It is unclear what limits the dispersal of Z. japonica seeds. Of the seeds that were incorporated into the sediment few germinated (5% or less). When seeds were planted in buckets placed into the sediment, with and without Z. marina, Z. japonica was able to germinate, grow, and reproduce in one year throughout the study area. Seedlings that emerged earliest (in April) either did not establish or did not survive as long as those seedlings that emerged later in May and June. Seedlings were often found uprooted, floating in the water. The rim of the buckets and the presence of Z. marina shoots appeared to protect the Z. japonica seedlings, preventing uprooting, but the results were not conclusive. Once seedlings became established, they spread vegetatively at a rapid rate and can persist throughout the winter, either as reduced shoots or as overwintering rhizomes. These overwintering plants contribute greatly to the following year's population.Science, Faculty of
Botany, Department of
Graduate
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FitzGerald, Véronique Chartier. "Ectomycorrhizal fungal assessment of South African Pinus patula seedlings and their biological control potential to enhance seedling growth". Thesis, Rhodes University, 2019. http://hdl.handle.net/10962/67902.
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Jernigan, Marcus B., Mitchel P. McClaran, Sharon H. Biedenbender i Jeffrey S. Fehmi. "Uprooted buffelgrass thatch reduces buffelgrass seedling establishment". TAYLOR & FRANCIS INC, 2016. http://hdl.handle.net/10150/616972.
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Buffelgrass (Pennisetum ciliare (L.) Link), a non-native perennial bunchgrass, invades ecologically intact areas of the Sonoran Desert. It competitively excludes native plants and increases fire frequency and intensity. Since the 1990s, whole buffelgrass plants have been manually uprooted and removed to control the invasion in southern Arizona. Uprooting plants results in bare, disturbed soil which promotes buffelgrass seed germination. This study examined whether leaving entire uprooted buffelgrass plants (thatch) on a field site reduces future buffelgrass establishment compared to removing uprooted plants from the site. A secondary goal was to determine whether light reduction and autoallelopathy were major factors in the negative effect of thatch on buffelgrass seedling density. Field plots with an average of 8,095 kg/ha thatch had 1.9 buffelgrass seedlings/m(2) which was significantly fewer than the 2.9 seedlings/m(2) in plots without thatch. Thatched portions of thatch plots (50% of their total area) had only 0.7 seedlings/m(2). In the greenhouse, which reduced outdoor light intensity by 35.2%, buffelgrass seeds sown in bare soil resulted in significantly higher seedling density than beneath buffelgrass thatch. Potential autoallelopathic chemicals leached from partially decomposed buffelgrass thatch and leached thatch had an intermediate but not significant (p = 0.09) effect on seedling numbers. Results suggest that leaving uprooted buffelgrass plants has the benefit of reducing seedling establishment in the area disturbed by uprooting.
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McKimmie, Tim, i Albert Dobrenz. "Salt Tolerance During Seedling Establishment in Alfalfa". College of Agriculture, University of Arizona (Tucson, AZ), 1987. http://hdl.handle.net/10150/203790.
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Deposition of salts from irrigation water is an increasing concern for Arizona farmers and agronomists. Selection for salt tolerance during the seedling stage has been undertaken over the past three years. Yield tests were conducted in greenhouses and a significant increase in dry matter production was shown in the selected material.
12
Elver, Harry 1961. "Factors affecting seedling mortality in Haitian agroforestry". Thesis, The University of Arizona, 1990. http://hdl.handle.net/10150/278449.
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The purpose of this study was to assess the correlation between (1) selected seedling conditions and (2) the participating farmers' knowledge of planting techniques and the seedling mortality of trees supplied by the Pan American Development Foundation's Agroforestry Outreach Project in Haiti. During the spring of 1990 planting season, 18 sample farmers and the trees they received were studied to determine the correlation of several seedling conditions with seedling mortality. Rootball condition, leaf drop, plant turgor, and internal box temperature were measured during seedling transportation from nursery to the field. The farmers' knowledge of planting techniques was determined by a test over a planting guide. The most significant findings were that the seedling mortality was not strongly correlated to either the individual conditions measured or the farmers' knowledge of planting techniques. Collectively, these seedling conditions accounted for approximately 25 percent of the total variation in the seedling mortality.
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Kilaru, Aruna, i Kent D. Chapman. "N-Acylated Phospholipid Metabolism and Seedling Growth". Digital Commons @ East Tennessee State University, 2012. https://doi.org/10.4161/psb.21314.
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N-Acylphosphatidylethanolamines (NAPEs) are precursors of endogenous bioactive lipids, N-acylethanolamines (NAEs). NAPEs, which occur as a minor membrane lipid, are hydrolyzed in a single enzymatic step catalyzed by a type of phospholipase D (PLD) to generate fatty acid ethanolamides. Although, the occurrence of NAPE is widespread in the plant kingdom, the physiological roles remain under appreciated due to the lack of sensitive tools to quantify the pathway metabolites. In Kilaru et al. (2012, Planta, DOI 10.1007/s00425-012-1669-z), comprehensive mass spectrometry (MS)-based methods were developed to gain a clearer understanding of the complex network of metabolites that participate in NAE metabolic pathway. This targeted lipidomics approach allowed insights to be drawn into the implications of altered NAE levels on NAPE content and composition, and the overall regulation of PLD-mediated hydrolysis in Arabidopsis. Based on these results, we point out here the important need for the identification of the precise isoform(s) of PLD in plants that is (are) involved in the regulated hydrolysis of NAPE and formation of NAE lipid mediators in vivo.
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Lindén, Elin. "The development of established shrub seedlings in persistent historical reindeer milking grounds". Thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-98888.
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This study focuses on how established shrub seedlings (Salix myrsinifolia x phycilifolia and Vaccinium vitis-idaea) develop in historical milking grounds. Historical milking grounds are cultural remains from the intensive reindeer herding era when the Sami migrated with closely controlled herds. Although the places were never fenced, the high concentration of reindeer close to the tenting grounds created patches of grass and forb dominated vegetation in areas outherwise dominated by deciduous or ericoid shrubs. Despite about 100 years of abandonment the shrubs have not come back and the milking grounds are still clearly visible in the landscape. One theory why the former milking grounds are so stable is that shrubs cannot establish from seedlings due to unfavorable abiotic conditions, or due to competitive dominance of already established forbs and grasses. I tested this hypothesis by planting shrub seedlings in the milking grounds and in reference areas, with and without neighboring vegetation and investigated seedling survival and growth. The results show that shrub seedlings are able to both survive and develop in milking grounds suggesting that the seedling state is not the limiting factor in shrub encroachment in the milking grounds.
15
Welling, P. (Pirjo). "Regeneration by seeds and vegetation structure in alpine plant communities, subarctic Finland". Doctoral thesis, University of Oulu, 2002. http://urn.fi/urn:isbn:951426861X.
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Abstract
The aims were to examine the importance of regeneration by seeds, the
influence of plant traits and disturbances, and the role of seed-seedling
conflicts in regeneration and in the determination of vegetation structure.
The study was carried out at in a subarctic alpine area (Kilpisjärvi
69°01'N 20°50E', Finland).
Seed bank and seedling densities were high in many plant communities
(ranges 99 -1109 viable seeds/m2 and 0.2-227
seedlings/m2, respectively). Effective seedling
recruitment is reflected in vegetation as a high proportion of plants with
poor or no vegetative reproduction ability. This development may take place
in meadows and snowbeds where herbs (e.g. Gnaphalium
supinum, Sibbaldia procumbens,
Veronica alpina and Viola
biflora) are abundant. On the other hand, the low proportion of
these plants in heath vegetation reflects ineffective seedling
recruitment.
Floristic similarities between the consecutive phases in the
regeneration pathway may be low despite effective seedling recruitment.
Clonality, large and small seed sizes and appendaged diaspores limit the
movement of species from phase to phase.
Generally, disturbances facilitate effective regeneration by seeds.
Grazing promotes species with large seed banks and is therefore one reason
for high seed bank densities. Freezing and melting processes negate a
negative influence of altitude on seed bank densities in the phase of
seedlings. However, if disturbances are severe and continuous and the soil
is compact, unstable or dry, disturbances are not beneficial. The same is
true if there is a shift in the species composition of seedlings from gaps
to closed vegetation. This phenomenon occurred in a rich meadow.
Seed-seedling conflicts limit regeneration by seeds in low-herb
snowbeds and Ranunculus glacialis-Gymnomitrion
snowbeds. Vegetative reproduction and infrequent pulses of seedling
recruitment negate an influence of short-term seedling recruitment on the
spatial structure of vegetation. Extreme conditions, such as low
temperatures, instability of the soil and late snowmelt modify the
influence of factors that are important in more moderate conditions.
To conclude, all transitions limit regeneration by seeds. However,
favourable conditions (e.g. moist conditions in a meadow) partly eliminate
the obstacles against seedling emergence. Regeneration by seeds therefore
has a major impact on the dynamics and structure of vegetation. In heath
vegetation, where bare soils are dry and the moss cover is thick, large
seed banks and seed rains do not guarantee effective seedling recruitment.
The regeneration process is reduced in the early phases, and plants that reproduce primarily by seeds have a minor role in vegetation. The accumulation of seed banks is effective in these circumstances.
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Roman, Erivelton Scherer. "Modelling seedling emergence of common lambsquarters in corn". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq31897.pdf.
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Mansor, Asyraf. "Determinants of Seedling Recruitment in Mimosa Pigra L". Thesis, Imperial College London, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.506819.
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Mimosa pigra L., a semi-aquatic woody legume, is a well known invasive plant in the tropics. Originating from Latin America, this species has spread to various localities around the globe and caused serious problems, both environmental and economical, in its new environment. I carried out a survey to assess the current status of Mimosa infestation in Peninsula Malaysia. Manipulative field experiments on the effect of soil disturbance, competitor identities, sown seed densities and defoliation on Mimosa seedling recruitment and survival were conducted as well. I found that although disturbance may not be an essential factor for seedling emergence in Mimosa, it significantly increase seedling establishment and survival. Recruitment in Mimosa was negatively affected when seedlings were grown together with vine (Centrosema) and creeper (Ipomoea), suggesting the importance of interspecific competition in reducing seedling emergence and establishment. The seed-sowing treatment showed that recruitment in Mimosa was both seed-limited and microsite-limited. While the number of seedlings emerging increased with the density of sown seeds, the proportion of emergence remained constant across the sown seed densities. Herbivory (through artificial defoliation) reduced seedling survival in Mimosa, although some seedlings proved to be resilient to even the highest intensity and frequency of defoliation. In general, I argued that Mimosa invasion in Peninsula Malaysia is not a serious problem since its populations were mostly restricted to disturbed ground and abandoned land. I would like to suggest that current best course of option is to continue monitoring its population and evaluate its spread, as control of established stands without destruction of the seed bank is likely to cause insignificant impact on subsequent population. One recommendation is to restrict the movement of topsoil from Mimosa infested sites. Future researches, if they were to be conducted shoUld try to establish method(s) that will reduce the Mimosa seed bank.
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McAdam-O'Connell, Darren John Patrick. "Agrobacterium-mediated genetic modification of Bramley's seedling apple". Thesis, Queen's University Belfast, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.396078.
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McKight, Shona Elizabeth. "Effects of Bacillus subtilis on cotton seedling development". Thesis, University of Nottingham, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385943.
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Clarke, Jodie Johnson. "Development of a Greenhouse Tobacco Seedling Performance Index". Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/33863.
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Tobacco seed performance is traditionally measured as percentage
germination at 14 d under controlled laboratory conditions. However, under
greenhouse conditions, seed lots with equal 14-d germination may exhibit
substantial differences in uniformity of early seedling growth and spiral root
incidence that impact the number of usable transplants. A seedling performance
index (SPI) was developed to quantitatively describe greenhouse tobacco seedling
performance. The 14-d emergence, relative leaf area uniformity, and seedling leaf
area determined by computer image analysis were used to calculate the index.
Greenhouse tobacco seed trials demonstrated that seed with the Rickard pellet had
higher emergence, but the higher spiral root incidence associated with the Rickard
pellet lowered the SPI compared to the Cross Creek pellet. Primed seed lots of
flue-cured cultivars (NC 72 and NC 71) had a significantly higher SPI than the
nonprimed seed lots at one location but not at a second location. Seed lots sown
in Premier Pro-Mix TA commercial medium had a higher spiral root incidence,
which resulted in a lower SPI compared to Carolina Choice, Carolina Gold, and
Sunshine LP5 commercial media. The index quantitatively determined
differences in seedling performance under greenhouse conditions not reflected by
standard germination tests. Significant differences in the SPI were observed
among seed lots with certified 90% germination. The SPI is a simple method to
describe seedling performance because the data used to calculate the SPI is
obtained from one seed tray image. In contrast, frequent counting and seedling
evaluations are involved with standard germination and vigor tests.Master of Science
21
Mustart, Penny. "Seed and seedling ecology of four Agulhas Proteaceae". Doctoral thesis, University of Cape Town, 1991. http://hdl.handle.net/11427/9671.
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Includes bibliographical referencesSerotinous (canopy-stored seed) Proteaceae, Protea obtusifolia and Leucadendron meridianum occur on shallow, alkaline soils overlying limestone, and P.susannae and L.coniferum on adjacent, deep, weakly acidic sands, in fire-prone fynbos. Seed reciprocal transplants were used to test whether regeneration niche requirements were determinants of adult distributions. There were no germination niche differences, but limestone species showed greater seedling mortality on the transplanted colluvial sands than limestone. There were also greater relative growth rates of seedlings on their own soil than counterparts on transplanted soil.
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Sinclair, John. "Crusting, soil strength and seedling emergence in Botswana". Thesis, University of Aberdeen, 1985. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU363198.
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This thesis gives the results of an investigation of the strengths and particularly the crust forming potential of arable soils from Botswana and the relationship to seedling emergence of sorghum, the most important crop in Botswana and one that because of its small seed weight (about 2 0 mg) can fail to emerge through a hard soil crust. A review of the literature suggested that the soil factors which had to be considered were dispersibility of clay and factors which affect this, and the bulk density of the soils. Soils which are found in many tropical and sub-tropical regions, with low organic matter and inactive clays can set hard after a simple wetting and drying cycle. In these soils, the strength is very strongly dependent on the water content, showing a hyperbolic or exponential relationship-, and the strengths when dry may be very greatly increased by remoulding the wet soil. The crust strength required to prevent seedling emergence varies with the size of the seedling and for cotton (seed weight about 80 mg), 1-3 MPa penetration resistance measured with a penetrometer is sufficient to prevent emergence. Seedlings exert a total force proportional to their number. In the experimental programme, seedlings' forces were measured, seedling emergence observed in a field experiment under crusting conditions, and the strength characteristics of a group of soils, representative of arable soils in Botswana, studied. A sorghum seedling was found to exert a maximum force of about 1 N or dividing by the area of the plumule, a pressure of about 0,5 MPa. The field experiment showed that much better emergence was obtained from planting 15 seeds together than from planting 4 seeds together when a crust formed after planting. A study of 32 soils, most of them sand to sandy loam in texture but with a few clays and hydroirorphic soils, from arable areas in Botswana showed the sandy to sandy loam soils to have high bulk densities ( 1,45-1 ,75 Mg/m3) and extremely low organic carbon contents (0,12-0,85 g/100g). The bulk densities of all the soils were inversely related to the organic carbon content and this was itself related to the clay content of the soils. The bulk densities of the sands were dependent on the grading of the sand fraction. Many of the soils were sensitive to remoulding in the Emerson test and the sands to loany sands had 0,4-1,0 g/100 g water dispersible clay. Measurements of tensile strength on air-dry samples showed that all the soils, except for one sand, set hard after a wetting and drying cycle, giving for vacuum wet samples indirect tensile strengths 1,0-14,4 kPa. For the sands to sandy loams this strength was related to the water dispersible clay content. Samples wet at atmospheric pressure were weaker than the vacuum wet samples, the reduction in strength was related to the air porosity of the non-vacuum wet soils prior to drying. Remoulding the soils prior to drying them increased the strength by a factor of up to 50 times, giving strengths from 4 kPa to 600 kPa. The strength after remoulding was dependent on the Emerson index. Compacting the soils increased their strength greatly and to an extent that agreed with the hypothesis that the strength obtained was proportional to the area of contact between the particles. Experiments on penetration resistance at a range of water contents were performed on a few soils. A hyperbolic relationship between water content and penetration resistance of the surface soil was found for sand to sandy loam soils, with the maximum resistance of dry soils above 2 MPa. The penetration resistance of the sandy loam soil was Increased three times by disturbing it when wet. Sprinkler wetting the sieved soils was not found to affect the penetration resistance by a large amount compared and other methods of welting. Penetration resistance was measured on air-dry samples of most of the main group of soils following varying degrees of wetting with a rainfall simulator. The clays and hydromorphic soils gave very low values of penetration resistance under these conditions, showing that at organic carbon contents of about 1% and clay contents from 20 to 30%, the decreased bulk density and tendency to form aggregates' on drying overcame the tendency to set hard. The mean values for the sands to sandy loams were from 1 to 6 MPa so all these soils could offer significant resistance to a sorghum seedling. The penetration resistance of the sands and loam/ sands depended on their bulk densities and water dispersible clay contents, while the penetration resistance of the sandy loams depended only on the water dispersible clay content.
23
Fessehazion, Melake Kessete. "Predicting and improving seedling emergence of three vegetable crops". Pretoria : [s.n.], 2005. http://upetd.up.ac.za/thesis/available/etd-02092006-130454.
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Bloomberg, Mark. "Modelling germination and early seedling growth of radiata pine". Lincoln University, 2008. http://hdl.handle.net/10182/681.
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Background: This study seeks to model aspects of the regeneration of radiata pine (Pinus radiata D.Don) seedlings under a range of environmental conditions. This study investigated whether “hybrid” mechanistic models, which predict plant growth and development using empirical representations of plant physiological responses to the environment, could provide a realistic alternative to conventional empirical regeneration models. Objectives: The objectives of this study were to 1) identify the functional relationships between the environmental conditions controlling germination, establishment and growth of radiata pine seedlings, under a range of those environmental conditions as specified by temperature and available light and soil water; and 2) specify those functional relationships in hybrid mechanistic (“hybrid”) models. Methods: Radiata pine seedling germination and growth were measured under controlled environmental conditions (incubators for seed germination, growth cabinets for seedlings), and results used to adapt, parameterise and test two published hybrid models; one for germination (the hydrothermal time model); and one for seedling growth in the first six months after germination, based on plant radiation use efficiency (RUE). The hydrothermal model was tested by incubating commercial radiata pine seeds under factorial combinations of temperature and water potentials where germination was likely to occur (12.5 ºC to 32.5 ºC and 0 MPa to –1.2 MPa.). 100 seeds were germinated for each factorial combination. The hydrothermal germination model was fitted to the germination data using non-linear regression modles, will allowed simultaneous estimation of all modle parameters. Seedlings were grown in controlled growth cabinets, and their RUE was calculated as the ratio of net primary production (NPP, specified in terms of an increase in oven dry biomass), to PAR intercepted or absorbed by a seedling. Estimation of seedling RUE required development of novel techniques for non-destructive estimation of seedling oven dry weight, and measurement of PAR interception by seedlings. The effect of varying PAR flux density on RUE was tested by measuring RUE of seedlings grown at 125, 250 and 500 µmol m⁻² s⁻¹. In a second experiment, the effect of deficits in available soil water on RUE was tested by measuring RUE of seedlings grown under 250 µmol m⁻² s⁻¹ PAR flux, and at different levels of available soil water. Available soil water was specified by a soil moisture modifier factor (ƒθ) which ranges between 1 for moist soils and 0 for soils where there is insufficient water for seedling growth. This soil moisture modifier had not previously been applied in studies of tree seedling growth. Temperatures for both seedling experiments were a constant 17.5 ºC (day) and 12.5 ºC (night). Results: Hydrothermal time models accurately described radiata pine seed germination. Model predictions were closely correlated with actual seed germination over the full range of temperature and water potentials where germination was likely to occur (12.5 ºC to 32.5 ºC and 0 MPa to –1.2 MPa. The minimum temperature for germination (base temperature) was 9.0 ºC. Optimum temperatures for germination ranged from ~20ºC for slow-germinating seeds to ~27 ºC for the fastest germinating seeds. The minimum water potential for seed germination varied within the seed population, with an approximately normal distribution (base water potential = –1.38 MPa, standard deviation of 0.48 MPa). In the process of developing the model, a novel explanation for the decline in germination rates at supra-optimal temperatures was developed (Section 3.4.6), based on earlier models proposed by Alvarado & Bradford (2002) and Rowse & Finch-Savage (2003). This explanation was that the decline in germination rate was not driven just by temperature, but by accumulated hydrothermal time above the base temperature for germination (T₀). This in turn raised the base soil water potential (Ψb) towards 0, so that the reduction in germination rate arose from a reduced accumulation of hydro-time, rather than from thermal denaturation of enzymes facilitating germination – the conventional explanation for non-linear accumulation of thermal time at supra-optimal temperatures for plant development. Upwards adjustment (towards 0 MPa) of base water potentials of germinating seeds occurred also at very cold temperatures in combination with high water potentials. In both cases (very cold or else supra-optimal temperatures) this upwards adjustment in base water potentials prevented germination of part of the seed population, and is proposed as a mechanism which enables seed populations to “hedge their bets” when germinating under less than ideal germination conditions. RUE of young germinated radiata pine seedlings growing in a controlled growth cabinet was not significantly different over a range of constant PAR flux densities. Mean RUE’s were 3.22, 2.82 and 2.58 g MJ⁻¹ at 125, 250 and 500 µmol m⁻² s⁻¹ respectively. In the second experiment, the novel use of a soil moisture modifier (ƒθ) to predict RUE of seedlings subjected to water stress proved successful within a limited range of soil water stress conditions. Measured seedling transpiration and stomatal conductance were closely correlated but seedling photosynthesis was less correlated with available soil water. This result suggests that photosynthesis was not coupled with stomatal conductance when PAR flux was 250 µmol m⁻² s⁻¹, which is well below saturating irradiance for C₃ plants. Conclusions: The use of hybrid, quasi-mechanistic models to describe tree seedling growth has been seldom explored, which necessitated the development of novel experimental and analytical techniques for this study. These included a predictive model of germination decline at sub- and supra-optimal temperatures; a method for accurately estimating seedling dry weights under a range of PAR flux densities; and a novel method for estimating light interception by small seedlings. The work reported in this thesis showed that existing hybrid models (the hydrothermal time germination model and the RUE model) can be adapted to model germination and growth of radiata pine seedlings under controlled environmental conditions. Nonetheless, further research is needed before the models can be confidently used as an alternative to conventional empirical models to model regeneration in “real-world” forests. Research priorities are the performance of hydrothermal germination models under variable field conditions, and the use of the soil moisture modifier for seedlings growing on a range of soil textures and under a range of PAR fluxes.
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Ganade, Gislene Da Silva. "Seedling establishment in Amazon rain forest and old-fields". Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339196.
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Carter, Sara Katherine. "TOLERANCE OF SEEDLING TURFGRASS SPECIES TO ALS INHIBITING HERBICIDES". UKnowledge, 2007. http://uknowledge.uky.edu/gradschool_theses/429.
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Acetolactate synthase (ALS) inhibiting herbicides are commonly used to eliminate weeds from mature turfgrasses. Field trials were conducted from 2004-2006, testing ALS herbicides for preemergence and early postemergence activity on newly seeded turfgrasses, using four species: Riviera bermuda, Zenith and Companion zoysia, L- 93 creeping bentgrass, and Poa annua L. Data collected were phytotoxicity and percent turf cover. Bermuda and zoysia herbicides were metsulfuron-methyl (42 g ha-1), trifloxysulfuron (29 g ha-1), flazasulfuron (53 g ha-1), foramsulfuron (30 g ha-1), bispyribac-sodium (112 g ha-1), and rimsulfuron (35 g ha-1). Treatments occurred the day of seeding and two-three weeks after seeding. Flazasulfuron, trifloxysulfuron and bispyribac-sodium caused significant damage in all treatments. Data suggests that bermuda and zoysia are tolerant of seedling treatments of foramsulfuron, rimsulfuron, and metsulfuron-methyl at these rates. Bentgrass and P. annua herbicides were foramsulfuron (15 and 30 g ha-1), siduron (2803 g ha-1), bispyribac-sodium (49 g ha-1), and paclobutrazol (281 g ha-1). Treatments occurred the day of seeding, two and four weeks after seeding. Foramsulfuron at 15 and 30 g ha-1 caused significant damage regardless of when it was applied. Data suggests that bentgrass and P. annua are tolerant of seedling treatments of siduron, paclobutrazol, and bispyribac-sodium at these rates.
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Agha, N. S. A. "High-density planting system for Bramley's seedling apple trees". Thesis, University of Reading, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373464.
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Jerram, Jonathan. "The role of membrane proteins in Arabidopsis seedling development". Thesis, University of Southampton, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.439381.
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Schutte, Brian J. "Biology and ecology of Ambrosia Trifida L. seedling emergence". The Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=osu1181937971.
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Baumer, Marilyn Cabrini. "Tree Seedling Establishment Under the Native Shrub, Asimina Triloba". Wright State University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=wright1183587955.
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Taylor, Anne. "Phototropism, traumatropism and blue light effects on seedling growth". Thesis, University of Aberdeen, 1987. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU010196.
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The growth events which are responsible for the phototropic curvature of seedlings towards blue light were investigated by growth analysis of seedlings of Avena sativa L. Time-lapse video analysis of coleoptiles given equivalent unilateral or bilateral blue light stimuli showed that both the duration and fluence-rate of the light treatments affected the growth responses which were recorded. The results suggest that the growth responses in bilateral light occur simultaneously with the growth changes which cause phototropic curvature, although they do not appear to make any contribution to the magnitude of curvature. Seedlings were also subjected to continuous unilateral microbeam (1mm) irradiation of discrete zones, to investigate whether 'message' transmission occurs in phototropism. The growth changes which occur in response to this treatment were recorded over the whole length of a 20 mm seedling, but began at different times in different zones. It was concluded that there must be some kind of 'message' transmission following perception of a phototropic stimulus in Avena. The kinetics of the response showed that it was unlikely that transmission could be simply due to tissue light-piping from the position of the original light beam. Unilateral irradiation of a small zone at the base of a coleoptile resulted in negative curvature. This experiment provided some evidence for acropetal transmission of the phototropic signal. A study was also made on the effects of wounding on the growth of Avena seedlings. This led to a re-evaluation of the significance of the traumatropic response to unilateral wounding. The experiments showed that even a slight wound can have severe effects on the growth of a coleoptile. The results are discussed in relation to previous theories on the mechanism of traumatropic curvature.
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Hahne, Kathryn S., i Ursula K. Schuch. "Nitrogen Requirements of Prosopis Velutina during Early Seedling Growth". College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2004. http://hdl.handle.net/10150/216532.
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The objective of this study was to determine the optimum rate of N to maximize growth of Prosopis velutina seedlings and minimize N leaching when seedlings were grown in different substrates. Mesquite seedlings were grown in sand or soilless media and were fertigated with a solution of67 % NH₄⁺: 33 % NO₃⁻ at a rate of 25, 50, 100, or 200 mg N/L. After 60 days, plants in media produced 41 % more leaves and total biomass compared to those in sand. Leaf number was greatest for plants grown at 200 mg N/L in both substrates. Root biomass of plants in media showed no response to increasing N concentrations while root biomass of seedlings in sand were similar for the three lower N concentrations and nearly doubled for the highest one. Shoot biomass of seedlings receiving 25, 50, or 100 mg N/L was similar, but more than doubled for plants fertigated with 200 mg N/L. N leachate losses were highest from seedlings growing in sand and receiving the two higher N fertigations, those in media had greatest N leachate loss when fertigated at 200 mg N/L.
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Abreu, F. M. S. G. "Influence of atmospheric saturation deficit on early growth of groundnut". Thesis, University of Nottingham, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378471.
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Stomph, Tjeerd Jan. "Seedling establishment in pearl millet (Pennisetum glaucum (L.) R.Br.) : the influence of genotype, physiological seed quality, soil temperature and soil water". Thesis, University of Reading, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.276632.
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Abdullah, Anwar Ahmad. "Micropropagation of Calabrian pine (Pinus brutia Ten.)". Thesis, University of Edinburgh, 1987. http://hdl.handle.net/1842/11453.
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Sheeter, Eric. "Mechanical silviculture". Thesis, Loughborough University, 1991. https://dspace.lboro.ac.uk/2134/10527.
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Problem: How to mechanise tree planting in North American logged sites? Trees are presently hand planted. Preliminary exploration identified the following collection of sub-problems. Vehicle: How to carry tools reliably and cost effectively over rough obstacle strewn ground? Results: U.S.A. - patent granted European Patent Office - patent granted Canada - patent granted The patents cover the main form and mode of operation of a simple but unconventional vehicle. Silvicultural/mechanical: How to mechanise the handling and placement of trees? Results: Two International Patents allowed. They cover a magazine/feed mechanism and a placement mechanism. They form a planting tool. One man guides the vehicle/tool system. An array of planting tools is carried. Two problems arise from the need to make guidance manageable and the planting rate fast enough. Spacing: How to cause the members of a collection of simultaneously operating tools to space themselves appropriately the spacing being driven by machine perceived cues? Choice: How to cause a tool to move to and halt over a plan table spot, tool action being driven by machine perceived cues? Results: One International Patent allowed. Spacing: A conceptual solution is described. Choice: A semi-automatic solution is described. It involves a system of tool guidance and a system of tool set-up, both light guided. Two methods for the detection of light signals in the presence of sunlight have been investigated. Choice-automatic; two solutions have been explored. One uses standard data processing, the other "parallel" processing. Here an idealised device is described which will compare for likeness two two-dimensional patterns.
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Ramirez, de Leon Hector. "Method of pollination and heritability for seedling vigor in switchgrass". Texas A&M University, 2005. http://hdl.handle.net/1969.1/2374.
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Switchgrass (Panicum virgatum L.) is a warm-season perennial bunchgrass native to North America. In addition to its importance as a forage grass, it has promise as a biofuel crop. However, its use is limited because the grass is difficult to establish. Improving seedling vigor is one approach for improving establishment. The objectives of this study were to: 1) select for increased seedling mass through half-sib family selection; 2) calculate an estimate of heritability for seedling mass; and 3) determine the mode of pollination of switchgrass. One cycle of selection was completed using a half-sib methodology. Seedling mass was determined in a series of growth chamber studies. The seed was produced in different space planted field nurseries in the College Station, TX area. Mean seedling weight of the base population (C0) was 0.014 gm seedling-1, while the mean seedling weight from the C1 cycle of selection was 0.029 gm seedling-1. Unfortunately, bulked seed from the base population was old and did not germinate well. Therefore, a new base population was recreated, and the C0 seedlings from this population were heavier than the C1 seedlings, 0.020 and 0.016 gm seedling-1,
respectively. The calculated heritability estimate was H2 = 0.6. Since the C0 and C1 nurseries were not grown on the same soil type, the lack of a positive response for seedling weight may be due to the different soil types. However, it may require another cycle of selection to determine if seedling mass can be positively impacted via half-sib selection. The mode of pollination of the species was determined by 1) observing pollen germination and tube growth in the pistils using fluorescent microscopy and 2) determining seed set with selfed plants. When self-pollinated, the pollen tubes never grew into the ovaries but when cross-pollinated the tubes readily grew to the micropyle. Also, when switchgrass plants were self-pollinated, viable seed were not produced. These findings indicate that switchgrass is highly self-sterile because a self-incompatibility mechanism prevents the pollen tubes from growing into the ovary of the same genotype.
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Izlar, Deborah Kay. "ASSESSMENT OF WHITEBARK PINE SEEDLING SURVIVAL FOR ROCKY MOUNTAIN PLANTINGS". The University of Montana, 2008. http://etd.lib.umt.edu/theses/available/etd-12272007-124748/.
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Whitebark pine (WBP) is a keystone species of Rocky Mountain alpine and subalpine areas. A pervasive non-native fungal disease (white pine blister rust), mountain pine beetle infestation, and successional replacement by shade-tolerant competitors following decades of fire exclusion have severely reduced whitebark pine and threaten these high-elevation ecosystems. Land managers are attempting to reverse whitebark pines decline by increasing regeneration of rust-resistant trees while restoring successional processes. Restoration efforts include the planting of whitebark pine seedlings and over 200,000 seedlings have been planted on National Forest, BLM and National Park service lands. In this Rocky Mountain (RM) study, select whitebark pine plantations were surveyed and seedling survival rates and ecological data collected. The purpose of this initial study was to determine overall survival rates for planted whitebark pine seedlings and to identify environmental conditions that have promoted high seedling survival. Data were analyzed at the site, plot and tree level. Microsites created by stumps, rocks and downed logs in close proximity to WBP seedlings greatly enhanced survival, seedling height and seedling growth during the first year after planting. Potential direct solar radiation was inversely related to WBP survival. Wet planting sites were detrimental to seedling survival. Results as to the effect of fire on seedling survival were inconclusive. However for 1st year seedlings it does appear that moderate, mixed or severe burning did result in much higher survival than unburned. To further understand the environmental conditions that affect seedling survival, an experimental planting was designed and monitored using the knowledge gained from the RM study. Seedling survival in this planting was statistically significantly associated with the presence of a microsite. And increased health of seedlings was associated with the presence of beneficial mycorrhizal associates. Only seedling located in burned or unburned whitebark pine communities were colonized with native fungi and colonization was higher for burned than for unburned sites. Whitebark pine seedlings are successfully being planted and it is possible to discern how different environmental conditions are affecting the survival, height, growth and health of planted seedlings.
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Barton, Kasey Elisabeth. "Seedling defense strategies: Effects of plant age, herbivory and competition". Connect to online resource, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3256440.
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McElhannon, Laura Michelle Waters Luther. "Enhancement of seed germination and seedling growth of Lenten rose". Auburn, Ala., 2008. http://repo.lib.auburn.edu/EtdRoot/2008/SUMMER/Horticulture/Thesis/Moore_Laura_47.pdf.
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Richardson, Ffiona. "Development of in vitro grafting technology for Bramley's Seedling Apple". Thesis, Queen's University Belfast, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324856.
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Peacock, Kenneth. "Growth, mechanical stress responses and mutation of sunflower seedling hypocotyls". Thesis, University of Aberdeen, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.277289.
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The aims of this thesis were four-fold: 1. To characterise the patterns of growth underlying established nutations of etiolated sunflower seedling hypocotyls. 2. To characterise the growth patterns and events surrounding the initiation of nutation in etiolated sunflower seedling hypocotyls. 3. To investigate the effects of applied compression and tension forces on the straight growth of etiolated sunflower seedling hypocotyls. 4. To investigate the relationship between auxin and the responses to mechanical stress in etiolated sunflower seedling hypocotyls. Time-lapse video analysis showed that the growth of etiolated sunflower seedling hypocotyls was more dynamic than expected, with growth constantly changing. When growth rates were plotted against time, the resultant curves showed regular oscillations similar to those of the movement traces for nutation and it was apparent that the nutational movements were intimately linked to the patterns of growth. Such patterns of growth were also found prior to the onset of nutation but in that case the growth curves on opposite sides of the hypocotyl did not oscillate out of phase with each other until immediately before the start of nutation. It was also found that there was a threshold height below which nutations were never found. The roles of light and geotropic responses in the initiation of nutation were also investigated. It was found that light was not required for nutation to occur and that various types of geotropic stimulation failed to initiate nutation in seedlings below the threshold height, although such seedlings were capable of responding to a gravity stimulus. It was concluded that the initiation and maintenance of nutation is an endogenous process and that nutation is a result of the way in which seedling hypocotyls grow rather than a discrete phenomenon superimposed on `normal' growth. The application of compression forces increased the growth of etiolated sunflower seedling hypocotyls over that of the non-compressed controls while tension forces applied to the same material did not produce any significant change in growth rates. When compression forces were applied to seedlings immersed in 10-10 Molar auxin solution the increase in growth due to compression were larger than those found for seedlings compressed while immersed in distilled water. It was concluded that some mechanism for the reception of compression forces operates in this material possibly involving a change in the sensitivity of the epidermal cells to auxin. A model was proposed in which growth is controlled by the mechanical forces acting on individual cells. It is suggested that nutation arises from the responses of cells and groups of cells to such mechanical strains.
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Hanley, Michael Edward. "The influence of molluscan herbivory on seedling regeneration in grassland". Thesis, University of Southampton, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296377.
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Newton, A. C. "Mineral nutrition and mycorrhizal infection of seedling oak and birch". Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306551.
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Bihzad, Mohammed Abbass Mohammed. "Ethylene, 2,4-D and seedling development in Cucurbita pepo. L". Thesis, University of Bristol, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333954.
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McGinley, Susan. "Temperature Makes the Difference: Improving Tomato Seedling Survival During Transport". College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2005. http://hdl.handle.net/10150/622186.
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Pereira, Marcelo Neiva. "Lettuce seedling production (Lactuca sativa L.) in floating hydroponic system". Universidade Federal do CearÃ, 2004. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=9218.
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Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgicoAlthough it had been early developed aiming to search on the plants mineral nutrition, the hydroponic gained more importance between the growers due to possibility a better nutritional control that confers greater plant quality and minor incidence of pests. Some hydroponic systems have been considered for the lettuce grown, between them NFT (Nutrient Film Technique) and Floating System. This last one consists of the use of great amounts of nutrient solution in tanks where the plants are floating on plates with its roots flooded. This system has been showing promising for hot climates where the high temperatures can to limit the growing in other systems as the NFT. Therefore, a trial was carried out to evaluate the floating system in its diverse characteristics as stability of the electrical conductivity and pH, availability of dissolved oxygen to the plants and temperature of the nutrient solution. Also was evaluated, through the total fresh weight and root length, the cultivars VerÃnica and Vera, which are spread out between the growers that use hydroponic systems, in regards to its adaptability to the floating system. Each one of the cultivars were submitted at two levels of electrical conductivity (1,5mS/cm and 2,5 mS/cm) and two levels of artificial aeration (20min/h and 60min/h) in split-split-plot design. The study showed that the cultivar Vera was significantly better than VerÃnica concerning to the total fresh weight and root length. It did not have significant difference between the studied levels of electrical conductivity and artificial aeration in the development of the plants. It could still be observed that the system revealed sufficiently steady in regards to the evaluated parameters.
Embora tenha sido desenvolvida primeiramente com o objetivo de pesquisar sobre a nutriÃÃo mineral das plantas, a hidroponia ganhou bastante importÃncia entre os produtores devido à possibilidade do controle nutricional mais estreito que confere maior qualidade Ãs plantas e menor incidÃncia de problemas fitossanitÃrios. VÃrios sistemas hidropÃnicos tÃm sido propostos para o cultivo de alface, entre eles o NFT (Nutrient Film Technique) e o sistema de leito flutuante (Floating System). Este Ãltimo consiste da utilizaÃÃo de grandes quantidades de soluÃÃo nutritiva dispostas em tanques onde as plantas ficam flutuando sobre placas de material leve com suas raÃzes imersas. Este sistema tem se mostrado promissor para climas quentes onde as altas temperaturas podem ser limitantes ao cultivo em outros sistemas como o NFT. Diante do exposto foi realizado trabalho no sentido de avaliar o sistema de leito flutuante em suas diversas caracterÃstica como estabilidade da condutividade elÃtrica e pH, disponibilidade de oxigÃnio dissolvido Ãs plantas e temperatura da soluÃÃo nutritiva. TambÃm foram avaliadas, atravÃs da matÃria fresca total e comprimento radicular, os cultivares VerÃnica e Vera, os quais sÃo os mais difundidos entre os produtores que utilizam o sistema hidropÃnico, quanto à sua adaptabilidade ao sistema de leito flutuante. Para isso cada cultivar foi submetido a dois nÃveis de condutividade elÃtrica (1,5mS/cm e 2,5 mS/cm) e dois nÃveis de aeraÃÃo artificial (20min/h e 60min/h) utilizando o delineamento em parcelas subsubdivididas. O estudo mostrou que o cultivar Vera foi significativamente superior ao VerÃnica em relaÃÃo à matÃria fresca total e comprimento radicular. NÃo houve diferenÃa significativa entre os nÃveis de condutividade elÃtrica e aeraÃÃo artificial estudados no desenvolvimento das plantas. PÃde-se observar ainda que o sistema mostrou-se bastante estÃvel em relaÃÃo Ãs variÃveis avaliadas.
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Conklin, Katie Lynn. "Aminocyclopyrachlor: Weed Control, Soil Dissipation, and Efficacy to Seedling Grasses". Thesis, North Dakota State University, 2012. https://hdl.handle.net/10365/26628.
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Aminocyclopyrachlor was developed for invasive weed control in non-cropland. Weed control, soil dissipation, and seedling grass tolerance with aminocyclopyrachlor were evaluated in field and greenhouse trials. Weed control was evaluated with aminocyclopyrachlor applied at 70 to 210 g ha-1. Absinth wormwood was controlled when treated during vegetative growth, but yellow toadflax was only controlled at flowering. Aminocyclopyrachlor alone did not control houndstongue. Aminocyclopyrachlor dissipation generally increased as either soil moisture or temperature increased. The DT50 values ranged from 3 to > 112 d. Aminocyclopyrachlor applied to cool season grasses at 91 to 112 g ha-1 provided adequate weed control and was safe for use on intermediate wheatgrass, but injured western wheatgrass. Efficacy to green needlegrass could not be determined. Big bluestem, sideoats grama, and switchgrass were difficult to evaluate due to poor grass establishment, but minimal injury was observed when aminocyclopyrachlor was applied at 91 to 168 g ha-1.
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Botha, Susan. "The influence of rainfall variability on savanna tree seedling establishment". Master's thesis, University of Cape Town, 2006. http://hdl.handle.net/11427/6238.
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Includes bibliographical references (leaves 111-114).My thesis investigates the rainfall requirements necessary for tree seedling survival of different savanna species in the first year of growth. Results from a field drought experiment showed that dry season survival for seedlings of Acacia nigrescens and Philenaptera vialacea was not related to wet season length. Instead mortality was highest immediately after germination despite irrigation to minimize dry spells. Furthermore there was no relationship between seedling size and the length of the dry spell seedlings of Acacia nigrescens and Philenaptera vialacea grown in basalt clay in the greenhouse, could survive. This was in contrast to seedlings of Scleracarya birrea and Terminalia sericea grown in granite sand, where number of dry days survived increased with number of growth days received. There was no significant differences in rainfall variability (t-test: tL III = 1.56, P = 0.121, F-ratio = 1.13) between a semi-arid (Satara) and semi-mesic (Pretoriuskop) site within the Kruger National Park despite significant differences in rainfall totals (t-test: tl, III = 4.40, P < 0.000, F-ratio 3.41). Results from a soil-water model show that seedling recruitment can occur at least twice a decade in the Satara area, which should be frequent enough to allow a transition to a woodland state over time. These results suggest that a mechanism other than the effect of rainfall variability on seedling establishment is required to explain the co-existence of trees and grasses at Satara. The lack of field germination, the absence of a seed bank and the germination of added seed at the field experiment site after rainfall emphasizes seed limitation as an important bottleneck at Satara. Higher herbivore biomass at Satara compared to Pretoriuskop may limit seedling establishment opportunities by destroying seed and seedlings of tree species.
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SHEN, CI-AN, i 沈慈安. "Study on the evaluation of seedling guality of dibbling-tube container seedlings". Thesis, 1989. http://ndltd.ncl.edu.tw/handle/91606682351978465570.
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