Dissertationen zum Thema „Wheat Growth“
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1
Zubaidi, Akhmad. „Growth and yield of durum and bread wheat“. Title page, contents and summary only, 1996. http://web4.library.adelaide.edu.au/theses/09A/09az93.pdf.
Annotation:
Bibliography: leaves 148-160. A series of experiments was conducted to examine the growth and nutrient uptake of durum and bread wheat at a number of sites in South Australia. The experiments examined response to water stress, the pattern of root and shoot growth, soil water extraction and nutrient uptake among a range of adapted bread wheat and durum wheat cultivars.
2
Ottman, Michael. „Predicting Wheat Growth Using the CSM-Cropsim-CERES - Wheat Crop Model“. College of Agriculture, University of Arizona (Tucson, AZ), 2008. http://hdl.handle.net/10150/203650.
Annotation:
CSM-Cropsim-CERES -Wheat is a crop growth model that predicts crop development stages, among other things, using genetic coefficients for vernalization and photoperiod. We used this model to predict flowering date for 12 durum varieties seeded in trials at Maricopa and Yuma from 1998 to 2006. The difference between simulated and measured flowering date averaged 4 days without genetic coefficients and improved to 3.5 days if genetic coefficients for flowering and vernalization were included for each variety.
3
Barczys, Cathleen. „THE EFFECT OF AUDIBLE SOUND FREQUENCY ON THE GROWTH RATE OF YOUNG WHEAT PLANTS“. Thesis, The University of Arizona, 1985. http://hdl.handle.net/10150/275379.
4
Hopkins, Laura. „The effects of elevated ultraviolet-B radiation on the growth and developmentof the primary leaf of wheat (Triticum aestivum L. cv Maris Huntsman)“. Thesis, University of St Andrews, 1997. http://hdl.handle.net/10023/13563.
Annotation:
Seedlings of Triticum aestivum L. cv. Maris Huntsman were grown for 7 days in a controlled environment chamber (16 hour photoperiod: PAR - photosynthetically active radiation), in the presence and absence of ultraviolet-B (UV-B: 280-320nm) radiation (+30% increase on ambient). UV-B resulted in a 17% reduction in leaf length due to changes in both the rate and duration of cell division and elongation. Measurements of the spatial distribution of cell division and elongation within the primary leaf were used to determine the temporal distribution of cells (i.e. cell age). The cell age gradient allows for the comparison of direct, and indirect UV-B responses, which result from the altered growth. Direct effects of UV-B included a reduction in chloroplast and mitochondrial transverse area, and an increase in chloroplast number, which suggests that UV-B affects organelle division. The developmental changes in protein content and amino acid free pools were increased as a direct result of UV-B treatment. In contrast, increases in chlorophyll content were due to an indirect effect of UV-B via altered growth. UV-B had no effect on the developmental changes in photosynthetic capacity and efficiency, and carbohydrate status of the primary leaf The primary leaf of wheat has provided a model system in which to examine the effects of UV-B on leaf development. This study highlights the need to consider cell age when determining the response of plants to UV-B.
5
Bond, Mark Anthony. „The effects of enhanced UV-B and CO2 on the growth and development of Triticum aestivum“. Thesis, University of St Andrews, 1997. http://hdl.handle.net/10023/13561.
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Seedlings of Triticum aestivum L. (cv Maris Huntsman) were propagated in a controlled environment chamber to 240hr (post-imbibition) under ambient, enhanced UV-B (200Wm-2), CO2 (550ppm and 700ppm) and combined UV-B/CO2 treatments. The grass leaf developmental model was used to determine changes in the cell-age gradient along the leaf length, under these treatments. By full leaf expansion, enriched CO2 had significantly increased leaf height, whilst this was decreased under enhanced UV-B, and decreased further under the combined UV-B/CO2 treatment. Analysis of the zones of cell division and cell elongation at the leaf base established that enriched CO2 increased mitotic activity and more so, cell elongation rates, whilst enhanced UV-B predominantly extended the duration of the cell division cycle. Under the combined UV-B/CO2 (550ppm) treatment it is proposed that cell division and cell elongation are greatly reduced at leaf emergence, but CO2-induced increases of cell division rates occur over time, prior to early cessation of leaf growth. The reduced leaf cell supply under enhanced UV-B+/-CO2 was accompanied by reductions in chlorophyll and protein synthesis at the leaf base, more so on a cell-age basis. Enhanced UV-B+/-CO2 did not alter the leaf Rubisco content. However, coleoptile Rubisco content was significantly reduced under enhanced UV-B, but this effect was ameliorated in combination with CO2. Large increases in UV-B-absorbing compounds accumulated along the leaf under enhanced UV-B+CO2 (550ppm), although this was attributed primarily to altered cell-age gradients rather than to UV-B induction per se. Analysis by Differential Display Reverse Transcription-PCR of the cell division zone has led to the isolation of 19 up-regulated and 11 down-regulated putative UV-B responsive transcripts. It is believed that the use of DDRT-PCR will further elucidate specific plant responses under these treatments.
6
Zahedi, Morteza. „Physiological aspects of the responses of grain filling to high temperature in wheat“. Title page, abstract and contents only, 2001. http://web4.library.adelaide.edu.au/theses/09PH/09phz19.pdf.
Annotation:
"June 2001." Includes bibliographical references (leaves 217-248). The effects of a sustained period of moderately high temperature on physiological and biochemical aspects of grain development were investigated in wheat cultivars grown under controlled environment conditions. The effect of variation in plant nutrition on the responses of cultivars to high temperature was also studied.
7
Caley, Clare Yvonne. „Termination of grain growth in cereals“. Thesis, University of Edinburgh, 1987. http://hdl.handle.net/1842/27746.
8
Miranda, L. N. de. „Aluminium-phosphate interactions in relation to wheat growth“. Thesis, University of Reading, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355697.
9
Arif, Hamayun. „Water relations of salt stressed wheat“. Thesis, Bangor University, 1990. https://research.bangor.ac.uk/portal/en/theses/water-relations-of-salt-stressed-wheat(b523794e-42f4-4165-bb35-11f07b7bbf28).html.
Annotation:
The present study was conducted to investigate the water relations of individual plant cells and the biophysical parameters controlling plant growth in the context of salt stress. Growth and water relations were studied in growing as well as in mature zones of the first emerged leaf of wheat seedlings (cv. Flanders, a British variety) in the context of NaCl stress. Various levels of NaCl (0,25,50,75,100,125 and 150 mol m) -3 were used to salinize the media. I In the case of leaf elongation rate a two phase response was found i. e. an immediate decrease and then, a recovery in the elongation rate. Leaf elongation rate decreased within 1-2 minutes of the onset of stress and, later, a recovery started 1-2 h after the salt addition. The time taken for the recovery was proportional to the levels of external salinity. After 24 h the elongation rate was almost fully recovered for all the NaCl concentrations. A similar response was observed when equi-osmolar concentrations (with NaCl) of mannitol were added to the media. In control plants turgor pressure of the expanding cells was about 0.45 MPa while tissue osmotic pressure was equal to 1.1 MPa showing that the cell had a low water potential (-0.6 MPa). The transpiration tension was equivalent to 0.1 MPa. Turgor pressure in th e growing cells did not change after the salt addition (0- 150 mol m-3 NaCl), however, the tissue osmotic pressure continuously increased with time. Turgor pressure dropped when more -3 than 150 mol m NaCl were applied to the media i. e. 200 and 250 mol m. -3 This is presented as evidence that growing leaf cells - maintained their turgor pressure In response. to . the salt stress by taking up osmotically -active solutes present in the cell wall. The salt stress had not any effect on Instron tensiometric measurements of elastic and plastic extension of the cell wall. A different turgor pressure response was found in the mature cells. Turgor pressure was about 1.0 MPa, almost twice that in the growing cells, while tissue osmotic pressure was similar to that found in the growing cells i. e. 1.1 MPa. After the application of the stress the turgor pressure dropped within 15- 20 min of the application of all the concentrations of NaCl. The osmotic pressure of osmotically active solutes present in the cell wall, nwr was almost negligible i. e. 4 0.1 MPa, in mature cells and so could not contribute to turgor maiýtenance. The extent of decrease was proportional to the external stress of 25, 50 and 75 mol m-3 NaCl only. Turgor pressure recovery, due to osmotic adjustment, started after about 10-12 h of the stress initiation. Complete turgor recovery was achieved after 24-48 h of the onset of stress depending on the applied NaCl concentration. Tissue osmotic pressure increased continuously with time. An increase in the nw was inferred during the whole experimental period and after 6d of the stress application that appeared to correspond to the magnitude of external stress. The concentrations of major ions and sugars were determined to measure their contribution towards the osmotic adjustment. Under control conditions Na +, ci-, PO 4 3- ' so 4 2- , glucose, fructose and sucrose were present in small amounts, while, K+ and No 3- were the-major osmotica. Their concentrations were about 200. mol _m-3. After the stress a large increase in the concentrations of Na + and Cl was observed, the sucrose concentration increased to a small extent. However, other osmotica remained Uniform for whole of the experimental time. A small decrease was observed in k+ concentration in response to higher salt levels. volumetric elastic modulus, -c, of mature cells was remained unchanged by the salt stress. However, the apparent resistance of the root cortex to osmotically driven water flow increased with the increase in stress level. No conclusion could be drawn about the contribution of these parameters to the control of growth and to leaf water relations in the context of salt stress. The possible use of turgor pressure recovery in the mature cells was investigated for assessing the extent of salt tolerance of various Pakistani wheat varieties. These varieties were previously rated according to their performance in absolute grain yield in response to NaCl stress. No simple correlation was found.
10
Deveson, M. R. „Effects of plant growth regulators on root growth and root/shoot integration in wheat (Triticum aestivum L.)“. Thesis, University of Reading, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376235.
11
Iqbal, Rana Muhammad. „Growth and physiology of spring wheat under saline conditions“. Thesis, Bangor University, 1992. https://research.bangor.ac.uk/portal/en/theses/growth-and-physiology-of-spring-wheat-under-saline-conditions(fadba57d-0627-4506-807a-e6c80792f57c).html.
Annotation:
A series of experiments were carried out in solution culture in growt~ ~ooms and a glasshouse, to study the effects of sallnlty on leaf extension rate ion concentrations, sap osmotic pressure, net photosynthesis and related parameters, stom~tal frequency, specific leaf weight and a number of agronomlc parameters of spring wheat. Rate of net photosynthesis, transpiration rate, stomatal conductance and sub-stomatal carbon dioxide concentration per unit area of leaf were determined using an Infra-red Gas Analyser. Experiments 1 and 3 were conducted in growth rooms set at a temperature cycle of 24°Cj16°C day and night and photoperiod of 16 hours. The seedlings received light from a bank of 125W fluorescent 'warm white' lights which provided between 200-300 ~mol m- 2 s-l photosynthetically active radiation at initial plant level. Experiments 2, 4 and 5 were carried out in a glasshouse with no control of light and temperature. In Experiment 1 the salinity treatments tested were control (0 mol m- 3 NaCI), 'constant' and 'variable' salinity. In the constant salinity treatment plants were grown at 100 mol m- 3 NaCI all the time after initial salt stress. In the variable salinity treatment a 12 day cycle was repeated with daily increments of 10 mol m- 3 NaCI after initial salt stress of 50 mol m- 3 NaCI till it reached to 150 mol m- 3 NaCI. During the final two days of the cycle salinity was stepped down from 150 to 100 to 50 mol m- 3 NaCl. In Experiment 2 the salinity levels tested were 0, 50, 100 and 150 mol m- 3 NaCI. CaCI was added in this and later experiments at 20:1 (mol Na~:mol ca2+) ratio. The results of the both Experiments 1 and 2 suggested that salinity had no effect on leaf appearance stage but tiller production was decreased. Salinity decreased leaf extension rate and final leaf length but leaf extension duration was not affected. Although leaf extension rate was the main factor influencing final leaf length, there were no consistent quantitative relationships between these parameters in different leaves and at different salinity levels. Plants in variable salinity performed better than those in constant salinity but these treatments were not significantly different and gave similar results. The results of Experiment 2 showed that a gradient of Na+ and Cl- concentrations was found in different leaves. Higher Na+ and Cl- concentrations were found in lower leaves than in expanding leaves. Calculated Na+ and CI- contents (ion concentrations x dry weight) suggested that these ions were mainly located in roots, stem and tillers irrespective of salinity levels. The effect of salinity was to increase concentrations of leaf Na+, Cl- and sap osmotic pressure in the youngest fully expanded leaves whereas K+ concentration was inconsistently affected. When gas exchange measurements were made in situ on leaves, light intensity showed wide i variation due to movement of clouds. Variations in light intensity and absence of any equilibration prior to measurements made it difficult to detect any effects of salinity on gas exchange. Therefore to determine the effects of salinity on gas exchange in expanding and senescing leaves, in Experiments 3, 4 and 5, a strong light source capable of providing photon flux densities at or near light saturation for gas exchange was used. In Experiments 3 and 4 light response curves were produced using neutral density filters. Using an exponential model, maximum net photosynthesis photosynthetic efficiency, photon flux compensation point and dark respiration for salinities and leaf insertions were calculated. In Exper~~ent 3 the .s~linity levels tested were 0, 100 and 200 mol m NaCI. Sa11n1ty decreased green lamina area, maximum and net photosynthesis, stomatal conductance, transpiration rate, leaf productivity but increased dark respiration and photon flux compensation point. Photosynthetic efficiency and transpiration efficiency were inconsistently affected. In Experiment 3 at 200 mol m- 3 NaCI leaf 6 senesced rapidly. Therefore in Experiment 4 the salinity levels tested were 0, 75 and 150 mol m- 3 NaCI. In Experiment 4 the parameters studied were identical to those in Experiment 3 except that the measurements were performed on leaf 5 and the flag leaf. In Experiment 4 a similar trend for gas exchange parameters was noted at 0 and 150 mol m- 3 NaCl but at 75 mol m- 3 NaCI Pn was higher than in the control due to delayed senescence. In both Experiments 3 and 4 leaf sap Na+, CI- and osmotic pressure increased and Pn decreased during senescence but there were no consistent relationships between these parameters for different leaves and salinity treatments. Experiments 2, 3 and 4 suggested that salinity increased stomatal frequency per unit leaf area but stomatal frequency per leaf and specific leaf weight were inconsistently affected. Experiment 5 was conducted to examine the effects of salinity on changes in gas exchange in the flag leaf and two penultimate leaves simultaneously. The salinity levels tested were 0, 75 and 150 mol m- 3 NaCI. The leaf x salinity interaction showed that salinity had larger effects on the flag leaf than leaves 2 and 3. The leaf x salinity interaction was significant for leaf temperature, net photosynthesis, stomatal conductance, transpiration rate and transpiration efficiency but not for sUb-stomatal carbon dioxide concentration. Salinity significantly decreased all the yield components and grain yield. The results of these experiments suggest that salinity had large effects on photosynthesis, dry matter production and grain yield and that ion concentrations do not determine the observed changes in net photosynthesis with leaf age in salt stressed plants.
12
Webb, Amanda Jane. „Mn, Cu and Zn requirements for wheat root growth“. Thesis, Webb, Amanda Jane (1992) Mn, Cu and Zn requirements for wheat root growth. PhD thesis, Murdoch University, 1992. https://researchrepository.murdoch.edu.au/id/eprint/52547/.
Annotation:
The effects of Mn, Cu and Zn deficiencies on the growth of the root system of wheat (Triticum aestivum cv. Gamenya) seedlings in solution culture were examined in three series of glasshouse experiments. Firstly, simple deletion experiments were undertaken in order to identify early root deficiency symptoms. Secondly, split root experiments were used to determine whether all of the root system requires an external supply of Mn, Cu and Zn; and thirdly, radioisotopes were used to investigate the extent of redistribution of Mn and Zn to roots without an external supply of Mn and Zn.
Since roots prepared using conventional procedures for microscopical examination were unsuitable for monitoring effects of nutrients on root anatomy, preliminary studies were undertaken to improve root preservation. Minimum shrinkage was achieved by reducing the osmolality of the primary fixative and increasing the period of resin infiltration using graded concentrations of resin.
In the deletion experiments, germinants were transferred (DO) into complete basal nutrient solution without either Mn, Cu or Zn for up to 25 days. Shoot and root Mn content and concentration were depressed in Mn-deficient plants as early as Day 5 (DS). Lignification of the cell walls of the root protoxylem was reduced at DlO, 5 days prior to a depression in root dry matter (DM) and expression of foliar deficiency symptoms. By D15, Mn deficiency depressed the length and number of seminal lateral roots, and by D20 had delayed nodal root formation, increased the number of lateral initials on the seminal root axes, and increased the distance from the root tip to the youngest emergent lateral root. The meristematic zone in roots of Mn-deficient plants was disorganized and highly vacuolated.
Withholding Cu led to reduced root protoxylem cell wall lignification, and decreased root Cu content and shoot Cu concentration (DIO), 9 days prior to foliar symptoms. By D25, Cu deficiency decreased root and shoot DM yield. the length of the seminal lateral roots and the nodal root axes, the number of lateral root primordia on the root axes. and increased the distance from the root tip to the youngest emergent lateral root.
Foliar symptoms of Zn deficiency were observed in Zndeficient plants on D9, one day prior to a depression in the Zn concentration of roots and shoots, and the Zn content of shoots. On D15, the root Zn content, root and shoot DM yield, root length, and root number were reduced in Zn-plants. Zn deficiency increased the thickness of the inner radial and tangential cell walls of the endodermis at D15. Furthermore, the size of the meristematic zone of Zn-deficient root tips was reduced and cells were highly vacuolated. By D20, the mean root length of lateral roots was depressed, and the distance from the root tip to the youngest emergent lateral root was reduced in Zn deficient plants.
In the second series of experiments, the effect of supplying one half of the root system with either Mn, Cu or Zn on root growth was examined using a split root system. The half of the root system without external Mn exhibited early symptoms of Mn deficiency; increased number of lateral initials/plant, increased distance from the root tip to the youngest emergent first order lateral root on the seminal axes, and reduced lignification of protoxylem in the young regions of the root. Supplying one half of a Cu-deficient root system with Cu caused renewed lignification of protoxylem cell walls in the younger regions of the roots supplied with external Cu, but did not ameliorate the decline in cell wall lignification in the part of the root system without an external supply of Cu. Withholding Zn from one half of the root system depressed the root Zn concentration and content, depressed the mean root length of nodal axes and lateral roots. These results suggest that Mn, Cu and Zn may be required in the rhizosphere for maximum root growth as retranslocation was insufficient to maintain normal root growth and development.
In the third series of experiments, the half of the root system grown continuously with complete nutrient solution was labelled with either roots without an external supply of either Mn or Zn was very low, and was estimated to be less than 1.0% of the total activity of the shoots. After the 24 h. uptake period 54Mn was present in the younger segments of the seminal root from the scutellar node, and after the 48 h. uptake period, 54Mn was present along the length of the seminal root from the scutellar node, and in the root tip of the seminal root. Autoradiography revealed a homogeneous distribution of 54Mn along the length of both seminal roots. By contrast the low levels of 65Zn were concentrated in the tips of Zn-deficient roots.
That Mn, Cu and Zn are not readily redistributed to roots of glasshouse grown wheat suggests that for plants in the field in which the shoot is adequately supplied with Mn, Cu and Zn, root growth may be limited into subsoils which are deficient, or have an uneven distribution of nutrients with very low phloem mobility.
13
Day, A. D., und M. J. Ottman. „Growth Cycle, Fertilizer, Planting Rate, and Genotype Influence Barley Hay or Forage Growth in the Southwest“. College of Agriculture, University of Arizona (Tucson, AZ), 1985. http://hdl.handle.net/10150/200506.
14
Artus, Sally. „VEGIGRO: a crop growth teaching model“. Thesis, University of Nottingham, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.484201.
15
Tunio, Shamsuddin. „Effect on environment and plant growth regulators on the growth of different wheat genotypes“. Thesis, Bangor University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293125.
16
Alghamdi, Mohammed A. M. „Plant growth regulators effects on vegative growth, yield and yield components in winter wheat“. Thesis, University of Reading, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.553077.
Annotation:
Three glasshouse experiments and one field experiment were carried out to investigate the effect of the plant growth regulator on vegetative growth and yield components of reduced height isogenic lines of the wheat (Triticum aestivum L.) cultivar Mercia. The first experiment compared the growth regulator response of seven isogenic lines of Mercia. Subsequent experiments used four lines, (Mercia control, Rhtl Rht2, and Rht8). Two glasshouse experiments examined the responses under well watered and water stress conditions. The third glasshouse experiment examined rates and time of application under well watered conditions, whilst the field experiment had different rates of application. In all experiments growth regulators reduced plant height significantly in all lines. Growth regulator decreased total dry matter and grain yield with greatest reduction generally for the control and Rht8 lines. Rhtl was the least affected. There were few significant effects of growth regulator on gas exchange and chlorophyll fluorescence but the trend was for greater values with growth regulator. In the first glasshouse experiment, a rate of 2.0 1 ha-1 applied just before the third node detectable stage under non water stressed and water stressed conditions gave slight increases in yield of up to 14% except for line Rht10 which increased significantly in non-stressed conditions. In the second glasshouse experiment, a rate of 2.5 1 ha" applied at the start of stem elongation under 30% FC and 100% FC gave reductions in yield up to 16% for the growth regulator and 55% under water stress. In the field experiment, rates of 2.5 and 3.0 1 ha-1 applied at the start of stem elongation gave reductions in yield up to 20% mainly through individual seed weight. In the final glasshouse experiment, rates of 2.5 and 3.0 1 ha-l applied at 6 leaves unfolded and 1st node detectable both reduced grain yield.
17
Tickes, B., und M. J. Ottman. „Evaluation of Plant Growth Regulators on Wheat in Arizona, 1987“. College of Agriculture, University of Arizona (Tucson, AZ), 1988. http://hdl.handle.net/10150/200841.
Annotation:
Plant growth regulators are applied to small grains to decrease lodging which can adversely affect crop growth and yield. Wheat is intensively managed in Arizona, and lodging can be a problem. Chlormequat and ethephon were applied at various rates and times in six studies in 1987 to evaluate their use on Arizona's semi -dwarf cultivars with respect to lodging plant height, yield components and grain yield The results indicated that growth regulators applied at the recommended rates and times may decrease plant height and decrease kernel weight. However, the influence of growth regulator treatments on tiller number, head number, kernel number, and grain yield was not demonstrated. The ambiguous results obtained suggest our efforts need to be directed toward documenting the extent of lodging in the state, studying the effects of lodging and predicting when lodging will occur.
18
Smallfield, B. M. „Influence of straw residues on the growth of winter wheat“. Thesis, University of Reading, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292951.
19
Ali, Mansab. „Light interception and growth of intercropped soybean into winter wheat /“. The Ohio State University, 1990. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487676261012395.
20
Ottman, M. J., S. H. Husman, R. J. Wegener, M. D. Sheedy, K. White und M. T. Rogers. „Critical Growth Stages for Water Stress in Durum, 2001“. College of Agriculture, University of Arizona (Tucson, AZ), 2001. http://hdl.handle.net/10150/205410.
Annotation:
The purpose of this research was to determine which durum growth stage is most responsive to additional irrigations (based on 35% depletion) when grown at a slightly suboptimal irrigation level of 65% plant available soil water depletion at other growth stages. A field experiment was conducted at the Maricopa Agricultural Center testing the effects of additional irrigations applied during tillering, jointing, or grain fill. Additional irrigations during tillering, jointing, grain fill, or no additional irrigations resulted in grain yields of 5964, 5419, 6301, and 4200 lbs/acre for Kronos and 5440, 5990, 5030, and 4019 lbs/acre for Westbred 881, respectively. The most responsive stage to additional irrigation was grain fill for Kronos and jointing for Westbred 881. The yield response of Kronos to additional irrigation during jointing may have been reduced by severe (78%) lodging in this treatment.
21
Ahmad, Manzoor. „Growth and gas exchange of wheat under saline and sodic conditions“. Thesis, Bangor University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245308.
22
Leverton, Ray. „Effects of competition and water availability on tillering and growth in wheat“. Thesis, University of Nottingham, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235732.
23
Ali, A. „The effects of environmental stresses on performance of spring wheat genotypes“. Thesis, Bangor University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382246.
24
Kgope, Barney Stephen. „Effects of sustained elevated CO2 concentration and Nitrogen nutrition on wheat (Triticum aestivum L. cv Gamtoos)“. Thesis, Rhodes University, 2000. http://hdl.handle.net/10962/d1003774.
Annotation:
There is consensus that high CO2 results in enhanced growth and yield for most crop plants. However, most of these studies were carried out in the presence of adequate nutrients, which is also the case in agricultural systems (managed ecosystems). About 20% of the earth’s land mass have sufficiently low levels of nutrients to cause some kind of stress to plants. On the other hand, elevated [CO2] decreases foliar nutrient elements in plants and as a result partitioning of certain nutrient elements in plants is altered. Little data is available on the partitioning of most nutrient elements in plants, and this will definitely impact on growth and yield. To investigate this, wheat (Triticum aestivum L. c.v. Gamtoos) was grown in controlled environment cabinets at 360 and 700 µmol mol -1 CO2. The full Long-Ashton nutrient solution comprising of three-nitrogen concentrations ([N]) viz. (4,6 and 12 mM) was used to water plants everyday. The measurement of net assimilation rate (NAR), stomatal conductance (gs), transpiration rate (E), water use efficiency (WUE), foliar [N], nitrogen use efficiency (NUE) and growth parameters (total plant biomass (TPB), total plant height (TPH), leaf area (LA), shoot and root dry weight) were made 7 days after germination (7 DAG) till the onset of flowering. The increase in nitrogen supply in the order of 4, 6 and 12mM resulted in an increase in NAR, g_s_ , WUE and a decline in E under elevated [CO2]. Under elevated [CO2] NAR was observed to increase during the first two weeks reaching its maximum at 14 DAG, thereafter followed by a decline reaching its maximum at 28 DAG. This was later followed by an increase at 35 DAG onwards. Under elevated [CO2], NAR was increased significantly between the nitrogen regimes during the first (7-14 DAG) and the last two (35-42 DAG) weeks. The response of assimilation as a function of internal [CO2] (Ci), showed a decrease with age at ages 14, 28 and 35 DAG. This negatively affected the initial slope and the CO2 saturated photosynthetic rates under all treatments. This suggest that acclimation may have been as a result of both stomatal and biochemical limitations. All the photosynthetic pigment levels (chl_a_, chl_b_, chl_(a+b)_, and C_(x+c)_ ) increased with an increase in nitrogen supply from 4 to 6mM [N]. A 12mM [N] resulted in a significant decline in the photosynthetic pigment levels compared to a 6mM [N]. Chla remained higher than chlb under all treatments. Also, NAR was seen to increase and decrease concomitantly with the photosynthetic pigment levels. Foliar [N] was seen to decrease with an increase in nitrogen supply from 4 to 6 mM [N] under elevated [CO2] and the effects were adverse under the 4mM [N]. Under the 6mM N regime foliar [N] was positively correlated to NAR for elevated [CO2] grown plants. Similarly, E was positively correlated to foliar [N] under the same conditions. Elevated CO2 and increase in nitrogen supply had a pronounced effect on total plant height (TPH), total plant biomass (TPB), leaf area (LA), shoot and root dry weight and nitrogen use efficiency (NUE). The effects were more pronounced under a 6mM [N] as a result of high NUE. However, under 12mM [N] growth was not as expected as a result of lower NUE. Under all treatments shoot dry weight (SDW) was positively correlated to NUE. Anatomical studies revealed that total leaf and midrib thickness was significantly increased with an increase in nitrogen supply under elevated CO2 to support the larger leaf areas. There were no significant changes in the chloroplast ultrastructure as a result of the increase in nitrogen supply and CO2 enrichment. Starch grain surface area was seen to decline with an increase in nitrogen under both ambient and elevated CO2. Elevated CO2 and increase in nitrogen supply significantly increased total grain dry weight per plant by 47 and 46% respectively under 6 and 12mM [N]. In contrast, the increase was by about 21, 61 and 67% respectively under 4, 6 and 12mM [N] between the CO2 regimes.
25
Waldron, Lucy Anne. „The nutritive value of different wheat varieties for broiler chickens“. Thesis, Open University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338547.
26
Shouyang, Liu. „Phenotyping wheat by combining ADEL-Wheat 4D structure model with proximal remote sensing measurements along the growth cycle“. Thesis, Avignon, 2016. http://www.theses.fr/2016AVIG0685/document.
Annotation:
La production agricole doit augmenter plus rapidement pour répondre à la demande alimentaire mondiale dans un avenir proche. Le phénotypage, c'est-à-dire la surveillance quantitative des variables de l'état des cultures et du fonctionnement quantitatif de la canopée, a été reconnu comme le goulot d'étranglement pour accélérer le progrès génétique et augmenter le rendement. Le phénotypage sur le terrain est obligatoire car il permet d'évaluer les génotypes dans des conditions naturelles de champ. Les progrès technologiques des capteurs, de la communication et de l'informatique favorisent le développement de systèmes de phénotypage à haut débit au cours de la dernière décennie. Toutefois, l'interprétation des mesures de phénotypage n' a fait l'objet que d'une attention limitée, ce qui a entraîné une sous-exploitation des potentiels des systèmes actuels. Cette thèse se concentre sur l'interprétation des mesures de phénotypage au champ sur les cultures de blé. Il comprend trois aspects complémentaires qui illustrent les potentiels du traitement d'image avancé, de l'inversion du modèle et de l'assimilation des données pour l'interprétation des mesures de phénotypage afin d'accéder à de nouveaux caractères ou d'améliorer la précision avec laquelle les caractères déjà accessibles ont été récupérés. Plusieurs plateformes (phénotypette, phénomobile, drones) et capteurs (caméras haute résolution RVB, LiDAR) ont été utilisés tout au long de cette étude. Les positions précises des plantes le long et à travers la rangée ont été décrites à partir d'images RVB haute résolution. Des modèles statistiques pour l'espacement des plantes le long du rang et la distance au centre du rang ont ensuite été proposés et calibrés. L'influence du profil de semis sur la fraction verte, facilement mesurable avec les techniques de phénotypage, a ensuite été évaluée. Le modèle statistique utilisé pour décrire la distribution de l'espacement des plantes le long de la rangée a été utilisé pour étudier la taille d'échantillonnage optimale et la méthode d'estimation de la densité des plantes. Enfin, une méthode a été mise au point pour estimer automatiquement la densité végétale à partir des images RVB haute résolution. Les résultats montrent une précision relativement élevée lorsque la résolution spatiale est suffisamment élevée et lorsque les observations sont effectuées avant que les plantes n'aient atteint trois stades de feuilles. Il est relativement facile d'obtenir une estimation précise du DG en utilisant des observations passives à un stade précoce. Toutefois, les performances se dégradent en cas de conditions DG élevées en raison du problème de saturation. L'utilisation du LiDAR avec sa capacité à apporter des informations sur la troisième dimension a été étudiée comme un moyen possible d'atténuer l'effet de saturation basé sur les régularités entre les couches supérieures et plus profondes de la canopée, comme décrit par le modèle ADEL_Wheat. Le LiDAR utilisé équipe la plate-forme de phénotypage phénomobile. Les résultats montrent une amélioration significative des performances lors de l'utilisation des observations LiDAR par rapport à l'estimation classique basée sur la fraction verte, assimilation de l'évolution temporelle des fractions vertes dans le modèle ADEL-Wheat. La surveillance de la dynamique de l'architecture de la canopée pour obtenir les premiers traits de vigueur de la culture est très recherchée par les sélectionneurs. Les résultats montrent que peu de paramètres du modèle ADEL-Wheat sont effectivement accessibles à partir de cette technique d'assimilation. De plus, il permet également d'estimer avec une bonne précision les propriétés émergentes de la canopée telles que le GAI et le nombre de tiges avec plus de 3 feuilles. Sur la base de ces résultats novateurs, des conclusions sont finalement tirées sur les limites de cette étude et sur les travaux futurs à entreprendre pour un phénotypage efficace sur le terrain à haut débitCrop production has to increase faster to meet the global food demand in the near future. Phenotyping, i.e. the monitoring crop state variables and canopy functioning quantitatively, was recognized as the bottleneck to accelerate genetic progress to increase the yield. Field phenotyping is mandatory since it allows evaluating the genotypes under natural field conditions. The technological advances of sensors, communication and computing foster the development of high-throughput phenotyping systems during the last decade. However, only limited attentions was paid in the interpretation of phenotyping measurements, leading to an under-exploitation of the potentials of current systems. This thesis focuses on advancing the interpretation of field phenotyping measurements over wheat crops. It includes three complementary aspects that illustrate the potentials of advanced image processing, model inversion and data assimilation for the interpretation of phenotyping measurements to access new traits or improve the accuracy with which already accessible traits have been retrieved. Several platforms (phenotypette, phenomobile, UAV) and sensors (RGB high resolution cameras, LiDAR) were used along this study.Characterization of the sowing pattern and density. The precise plant positions along and across the row was described from high resolution RGB images. Statistical models for the spacing of plants along the row and distance to the row center were then proposed and calibrated. The influence of the sowing pattern on the green fraction that can be easily measured with phenotyping techniques was then evaluated. The statistical model used to describe the distribution of plant spacing along the row was exploited to investigate the optimal sampling siz and method for plant density estimation. Finally, a method was developed to automatically estimate the plant density from the high resolution RGB images. Results show a relatively high accuracy when the spatial resolution is high enough and when observations are made before plants have reached 3 leaves stages.ADEL-Wheat model assisted Estimation of GAI from LiDAR measurements. It is relatively easy to achieve accurate GAI estimate using passive observations at early stages. However, the performances degrade for high GAI conditions due to the saturation problem. The use of LiDAR with its capacity to bring information on the third dimension was investigated as a possible way to alleviate the saturation effect based on the regularities between top and deeper canopy layers as described by the ADEL_Wheat model. The LiDAR used is equipping the phenomobile phenotyping platform. Focus was put on the stage of maximum GAI development when saturation effects are the largest. Results show a significant improvement of performances when using LiDAR observations as compared to classical green fraction based estimation.Assimilation of green fractions temporal evolution into ADEL-Wheat model. Monitoring the dynamics of canopy architecture to get early vigor traits of the crop is highly desired by breeders. The feasibility and interest of a phenotyping data assimilation approach was evaluated based on in silico experiments using the ADEL_Wheat model simulations. The green fraction observed from several view directions and dates is the variable that is assimilated. A sensitivity analysis was conducted to evaluate the effect of the number and spacing of the observation dates as well as the number of view directions used. Results show that few parameters of the ADEL-Wheat model are actually accessible from this assimilation technique. Further, it allows also estimating with a good accuracy emerging canopy properties such as the GAI and the number of stems with more than 3 leaves. Based on these innovative results, conclusions are finally drawn on the limits of this study and on the future work to undertake for efficient field high-throughput phenotyping
27
Haddad, G. A. „Influence of nitrogen on the growth of winter wheat on restored opencast land“. Thesis, University of Newcastle Upon Tyne, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377658.
28
Catley, Merryn Anne. „Studies of the genetic control of grain growth and the pattern of amyloplast DNA accumulation during the endosperm development in wheat“. Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235819.
29
Ehsanzadeh, Parviz. „Agronomic and growth characteristics of spring spelt compared to common wheat“. Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ37882.pdf.
30
Rajper, Inayatullah. „The effects of sodicity on the growth and yield of wheat“. Thesis, Bangor University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297714.
31
Vincent, Colin. „Effects of temperature on root growth and development of winter wheat“. Thesis, University of Reading, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286899.
32
Traynor, Mary. „Root growth in drying soil : a role for ABA?“ Thesis, Lancaster University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322894.
33
Matthews, Sharon Sarah. „The response of wheat to inoculation with the diazothroph Azorhizobium caulinodans“. Thesis, University of Nottingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368250.
34
Wiese, Jacobus Daniel. „The effect of crop rotation and tillage practice on soil moisture, nitrogen mineralisation, growth, development, yield and quality of wheat produced in the Swartland area of South Africa“. Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/80027.
Annotation:
Thesis (MScAgric)--Stellenbosch University, 2013.ENGLISH ABSTRACT: This study was done during 2010 and 2011 as a component study within a long-term crop rotation/soil tillage trial that was started in 2007 at the Langgewens Research Farm near Moorreesburg in the Western Cape Province of South Africa. The aim of this study was to determine the effect of crop rotation and soil tillage on the soil moisture content, mineral-N levels of the soil, leaf area index, chlorophyll content of the flag leaf, biomass production, grain yield and grain quality of spring wheat (Triticum aestivum L). The experimental layout was a randomised complete block design with a split-plot treatment design replicated four times. Wheat monoculture (WWWW), lupin-wheatcanola- wheat (LWCW) and wheat-medic (McWMcW) crop rotation systems were included in this study and allocated to main plots. This study was confined to wheat after medic/clover, wheat after canola and wheat monoculture. Each main plot was subdivided into four sub-plots allocated to four tillage treatments namely: Zero-till (ZT) – soil left undisturbed until planting with a star-wheel planter No-till (NT) – soil left undisturbed until planting and then planted with a no-till planter Minimum-till (MT) – soil scarified March/April and then planted with a no-till planter Conventional-till (CT) – soil scarified March/April, then ploughed and planted with a no-till planter. Soil samples were collected every two weeks from just before planting until before harvest, from which gravimetric soil moisture and total mineral-N (NO3--N and NH4+-N) were determined. Plant samples were collected every four weeks until anthesis, starting four weeks after emergence. From these leaf area index and dry-matter production were determined. Chlorophyll content and light interception were measured at anthesis. At the end of the growing season the total biomass, grain yield and grain quality was determined. Crop rotations which included medics (McWMcW) or canola/lupins (LWCW) led to higher mineral-N content of the soil at the start of the 2011 growing season when compared to wheat monoculture, but did not have an effect on soil moisture. Conservation tillage (minimum- and no-till) practices resulted in higher soil moisture whilst conventional-till resulted in the highest mineral-N content for 2010. There was however no differences in mineral-N content between tillage methods for 2011, whilst soil moisture content was affected in the same way as the previous year. Both crop rotation and tillage influenced crop development and biomass production. In general, increased soil disturbance together with wheat after medics and wheat after canola resulted in better development of the wheat crop with regards to dry matter production and leaf area index. The positive effect of medic and canola rotations was also evident on chlorophyll content and light interception. Grain yield was positively influenced by wheat after medics and wheat after canola, with both systems out-yielding wheat monoculture in 2010 and 2011. Minimum- and no-till resulted in the highest grain yield in both years. Crop rotation and tillage practice showed no clear trends with regards to grain quality. This illustrated the important effect of environmental conditions during grain-filling. Environmental factors such as rainfall and temperature had significant effects in both years of the study, but the importance and advantages of crop rotation, especially with a legume crop such as medics included, was evident even though this component study was done early in terms of the long-term study. The positive effect of implementing conservation tillage practices such as minimum- and no-till were also clearly shown in results obtained throughout this experiment.
AFRIKAANSE OPSOMMING: Die studie is gedurende 2010 en 2011 uitgevoer as ‘n deelstudie van ‘n langtermyn grondbewerking- en wisselbouproef op die Langgewens proefplaas naby Moorreesburg in die Wes-Kaap Provinsie van Suid-Afrika. Die doel van hierdie studie was om die effek van grondbewerking en wisselbou op grondvog, minerale stikstof in die grond, blaaroppervlakindeks, chlorofilinhoud van die blare, graanopbrengs en -kwaliteit van lente koring (Triticum aestivum L) te kwantifiseer. Die eksperiment is uitgelê as ‘n volledig lukrake blokontwerp met ‘n verdeelde perseel ontwerp met vier herhalings. Wisselboustelsels wat aan hoofpersele toegeken is sluit koring monokultuur (WWWW), lupien-koring-kanola-koring (LWCW) en medic-koring (McWMcW) in. Grondbewerking is toegeken aan subpersele. Die grondbewerkingsbehandelings het ingeslui: Zero-bewerking (ZT) – die grond is onversteurd gelaat en koring is met ‘n sterwielplanter geplant, Geen-bewerking (NT) – die grond is onversteur gelaat tot en met planttyd waar koring met ‘n geenbewerking (no-till) planter geplant is, Minimum-bewerking (MT) – die grond is in Maart/April met ‘n tandimplement bewerk en met ‘n geen-bewerking planter geplant, Konvensionele-bewerking (CT) – die grond is in Maart/April met ‘n tandimplement bewerk die grond is in Maar/April geploeg met ‘n skaarploeg en met ‘n geenbewerking planter geplant. Grondmonsters is elke twee weke versamel van net voor plant tot net voor oes. Vanaf die versamelde monsters is die grondwaterinhoud grawimetries bepaal en ook die totale minerale stikstofinhoud (NO3--N en NH4+-N). Plantmonsters is vierweekliks versamel beginnende vier weke na opkoms tot en met antese. Blaaroppervlakindeks en biomassaproduksie is bepaal. Die chlorofilinhoud en ligonderskepping is tydens antese bepaal. Aan die einde van die groeiseisoen is totale biomassa, graan opbrengs asook graankwaliteit bepaal. Wisselboustelsels, wat medics (McWMcW) of kanola/lupine (LWCW) ingesluit het, het ‘n hoër minerale stikstofinhoud aan die begin van die 2011 groeiseisoen getoon. Wisselbou het egter geen effek op grondvog gehad nie. Minimum- en geenbewerking het ‘n hoër grondvoginhoud tot gevolg gehad, terwyl die persele onder konvensionele bewerking ‘n hoër minerale stikstof inhoud gehad het in 2010. In 2011 was daar geen verskille in die minerale stikstofinhoud tussen verskillende die bewerkingsmetodes nie en grondvog gedurende 2011 is op dieselfde wyse as in 2010 beïnvloed. Beide wisselbou en bewerkingsmetode het ‘n invloed gehad op gewasontwikkeling en biomassaproduksie. Die algemene tendens was dat, soos grondversteuring toegeneem het in die koring na medics en koring na kanola, het beter gewasontwikkeling plaasgeving met betrekking tot droëmassaproduksie en blaaroppervlakindeks. Die positiewe effek van wisselbou is ook waargeneem in die chlorofilinhoud van die blare en die ligonderskeppingspotensiaal van die blaredak. Graanopbrengs is positief beïnvloed deur die wisselboustelsel, met beide koring na medics en koring na kanola wat hoër graanopbrengste as koring monokultuur vir beide jare gelewer het. Die hoogste graanobrengs is ook gekry onder die minimumen geen-bewerkingsbehandelings vir 2010 en 2011. Wisselbou en bewerkingsmetodes het geen duidelike invloed op koringkwaliteit gehad nie. Dit is ‘n weerspieëling van die belangrike invloed van omgewingsfaktore gedurende die korrelvulstadium van koring. Omgewingsfaktore soos reënval en temperatuur het betekenisvolle effekte in beide jare van die studie gehad, maar die belang van ‘n wisselbou wat ‘n stikstofbinder soos medics insluit, was reeds in hierdie vroeë stadiums van die langtermynproef opvallend. Die positiewe effek van minimum- en geen-bewerking was ook duidelik sigbaar gedurende die verloop van die studie.
The Western Cape Agricultural Trust for the opportunity and the finances to do this study
35
Malik, Iram. „The effects of ozone and salinity on wheat (Triticum aestivum L.)“. Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343901.
36
Pharudi, Joseph Albert. „Effect of mycorrhizal inoculation and phosphorus levels on growth and yield of wheat and maize crops grown on a phosphorus deficient sandy soil“. Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/5135.
37
Hossain, A. H. M. Sakhawat. „Mechanisation of wheat production in Bangladesh based on a growth modelling approach“. Thesis, University of Newcastle Upon Tyne, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241559.
38
Harris, Joanna Mary. „An assessment of bacterial inoculants of winter wheat (Triticum aestivum L.) under temperate conditions“. Thesis, University of Nottingham, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.330169.
39
Mulaudzi, Renolda Ipeleng. „Assessment of plant growth promoting rhizobacteria for plant growth enhancement and biocontrol activity against Fusarium pseudograminearum on wheat“. Diss., University of Pretoria, 2019. http://hdl.handle.net/2263/77860.
Annotation:
Plant growth promoting rhizobacteria (PGPR) are those bacteria that colonise the rhizosphere of various plants and promote growth either directly by improving nutrient uptake by the plant roots or indirectly through the control of pathogens. Due to the negative effects associated with the prolonged use of chemical fertilizers and fungicides, a lot of emphasis is now being given to research that investigates an alternative, sustainable and environmentally friendly method of crop production and protection. In the current study, a collection of rhizobacterial isolates from the University of Pretoria- Plant Growth Promoting Rhizobacteria (UP-PGPR) culture collection were screened for plant growth promotion and biocontrol activity against crown rot caused by Fusarium pseudograminearum on wheat (Triticum aestivum).
A seedling tray bioassay was utilised as a rapid small-scale method to screen the rhizobacterial isolates for biocontrol activity against wheat crown rot in the greenhouse. The same method was also used to screen the isolates for direct plant growth promotion of wheat. Of all the isolates (113) screened for wheat crown rot control, 52% (59 isolates) significantly increased the shoot dry weight of the seedlings, 41% (46 isolates) increased the root dry weight of the seedlings, and the total seedling dry weight was increased by 32% (36 isolates) of the isolates. A seedling bioassay was also used to screen the isolates for direct plant growth promotion of wheat. Of the 113 isolates screened, 12% (14 isolates) increased the shoot dry weight of the seedlings, 22% (25 isolates) increased the dry weight of the roots; while the total dry weight of the seedlings was increased by 32% (36 isolates) of the isolates.
Subsequent to the seedling bioassay in the greenhouse, the isolates were also assessed in vitro for selected traits associated with biocontrol activity and plant growth promotion. To test for a broad spectrum of biocontrol activity, in addition to F. pseudograminearum, the isolates were also screened for inhibition of Rhizoctonia solani, Phytophthora capsici and Macrophomina phaseolina. Almost 50% of the isolates displayed broad-spectrum activity against the pathogens on three different media. Some notable isolates in this regard were Bacillus sp. strain N54 and Pseudomonas sp. strain N59, N67 and N69. All isolates screened displayed multiple traits associated with biocontrol activity such as the production of antibiotic enzymes, volatiles (NH3 and HCN) and the production of siderophores. The isolates also displayed multiple traits associated with direct plant growth promotion (nitrogen fixation, phosphate solubilization, IAA and ACC deaminase). Based on the results obtained from the seedling bioassays in the greenhouse and the in vitro screening, a scoring system was developed, and the isolates were awarded points. Bacillus sp. strain A09AC, A17, A20, N02, N28, N54 Stenotrophomonas sp. strain A45, Pseudomonas sp. strain N04AC, N44 and N59A were selected for pot trials to confirm their F. pseudograminearum biocontrol efficacy (Figure 1.1). Bacillus sp. strain A10AC, Stenotrophomonas sp. strain A33, A43, A45, Paenibacillus sp. strain KBS1F3, Pseudomonas sp. strain N29, N69, N67, N76 and Pantoea sp. strain N34 were selected for use in pot trials in the greenhouse to confirm their efficacy as wheat growth promoters.
The selected isolates were further assessed for biocontrol activity and plant growth promotion in greenhouse experiments. KBS1F3 (Paenibacillus alvei) showed the best results for wheat growth promotion while A17 (Bacillus cereus) gave the best results for biocontrol activity. The effect of temperature, pH, NaCl and different carbon sources on the growth of the isolates was also assessed in vitro. The optimum temperature of all isolates was observed to be between 26oC and 35oC while KBS1F3 was able to grow at 47oC and A17 at 50oC. The growth of KBS1F3 decreased with an increase in NaCl concentration while A17 still grew well at 4% NaCl concentration. All isolates grew optimally at pH 7. KBS1F3 still grew well at pH 8 while A17 showed good growth at all pH values except pH 4. All isolates showed the ability to utilise a variety of carbon sources.Dissertation (MSc (Agric))--University of Pretoria, 2019.
Microbiology and Plant Pathology
MSc (Agric)
Unrestricted
40
Ottman, M. J., T. A. Doerge und E. C. Martin. „Late Season Water and Nitrogen Effects on Durum Quality, 1995 (Final)“. College of Agriculture, University of Arizona (Tucson, AZ), 1996. http://hdl.handle.net/10150/202421.
Annotation:
Durum grain quality is affected by many factors, but water and nitrogen are factors that the grower can control. The purpose of this research was to determine 1) the nitrogen application rate required at pollen shed to maintain adequate grain protein levels if irrigation is excessive or deficient during grain fill and 2) if nitrogen applications during grain fill can elevate grain protein. Field research was conducted at the Maricopa Agricultural Center using the durum varieties Duraking, Minos, and Turbo. The field was treated uniformly until pollen shed when nitrogen was applied at rates of 0, 30, and 60 lbs/acre. During grain fill, the plots were irrigated based on 30, 50, or 70% moisture depletion. In a separate experiment, nitrogen fertilizer was applied at a rate of 30 lbs N/acre at pollen shed only, pollen shed and the first irrigation after pollen shed, and pollen shed and the first and second irrigation after pollen shed. Irrigation had no effect on grain protein level, although increasing nitrogen rates at pollen shed from 0 to 30 and 30 to 60 lbs N/acre increased protein by 1 percentage point. Nitrogen fertilizer application at the first irrigation after pollen shed increased grain protein content from 10.4 to 11.4% and application at the first and second irrigation after pollen shed increased grain protein content further to 11.9% averaged over varieties. Irrigation management during grain fill may not play as large a role in controlling grain protein content as was originally thought except perhaps on heavy soils, and nitrogen fertilizer application during grain fill may not be too late to increase grain protein content.
41
Husman, S. H., und M. J. Ottman. „Intensive Cereal Management for Durum Production, Buckeye, 1996“. College of Agriculture, University of Arizona (Tucson, AZ), 1996. http://hdl.handle.net/10150/202422.
42
Knowles, Tim C., Michael J. Ottman und Rock Cramer. „Influence of Nitrogen Fertilizer Applied at Flowering on Durum Wheat Grain Yield and Quality“. College of Agriculture, University of Arizona (Tucson, AZ), 1996. http://hdl.handle.net/10150/202440.
Annotation:
Application of nitrogen (N) fertilizer in conjunction with the irrigation event occurring closest to the flowering stage is effective in reducing the incidence of yellowberry and boosting grain protein levels of durum wheat. However, N applications at this time normally do not increase grain yield, except perhaps on very sandy soils. A field experiment was conducted to determine the profitability of applying 35 pounds of N per acre at flowering to durum wheat to avoid dockage for poor grain quality. Two treatments consisted of a check plot with no N applied at flowering and UAN 32 water run at a rate of 35 lbs. N /acre to basin irrigated durum wheat grown on a loamy sand soil. Maximum durum wheat grain yield (6157 lbs. /acre), protein concentration (13.7 %), and corrected income per acre ($480.31) was obtained with the N fertilizer application. In fact, N fertilization at flowering on this sandy soil increased durum wheat grain yield by 255 lbs. /acre compared to the unfertilized plot.
43
Husman, S. H., und M. J. Ottman. „Nitrogen Fertilization of Durum Based on Stem Nitrate, Buckeye, 1996“. College of Agriculture, University of Arizona (Tucson, AZ), 1996. http://hdl.handle.net/10150/202441.
44
Tibbitts, Spencer A. „Effect of Silicon on Wheat Growth and Development in Drought and Salinity Stress“. DigitalCommons@USU, 2018. https://digitalcommons.usu.edu/etd/6925.
Annotation:
Silicon is a major component of most soils, and is found in significant concentration in plant tissue. Plants vary widely in the amount of silicon they take up, with some plants excluding it, and others using transporters to move the silicon from the soil into their roots. Early plant physiology studies were unable to determine conclusively whether silicon was essential to plant growth, but for some plants, most notably rice, it has proved to be important enough to justify fertilizing silicon deficient fields.
Researchers at the USU Crop Physiology Lab tested the effect of silicon on wheat growth and seed yield components. One study was grown in buckets of peat moss, with half the buckets being stressed with low water. The other study was grown in hydroponic tubs, with half the tubs being stressed with high levels of salt.
The results from these studies showed that silicon does increase wheat seed yield and vegetative mass. Wheat with low levels of silicon exhibited twisting of the awns and decreased roughness of leaf surfaces. Silicon also improved water efficiency of drought stressed plants, and affected the concentration of many micro- and macro-nutrients in leaf tissue.
45
Ntiamoah, Charles. „Effects of temperature, photoperiod, and vernalization on the growth, development, and predictions by the CERES-wheat model, for spring wheat cultivars“. Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/NQ62662.pdf.
46
Day, A. D., F. R. Katterman und J. R. Wilson. „Effects of an Extract from Municipal Wastewater on the Growth of Barley“. College of Agriculture, University of Arizona (Tucson, AZ), 1985. http://hdl.handle.net/10150/200514.
47
Fauzi, Mohamad Taufik. „The effect of growth regulators and nitrogen on Fusarium head blight of wheat /“. Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=69547.
Annotation:
Plant growth regulators and nitrogen fertilization have been associated with the increased incidence of fusarium head blight, a destructive disease of wheat (Triticum aestivum L.). In Canada, the major causal organism of this disease is Fusarium graminearum Schwabe, the conidial state of Gibberella zeae (Schw.) Petch. Most studies concerning the effect of plant growth regulators on fusarium head blight were conducted in fields with natural infection. The objective of this research was to evaluate the effect of growth regulators and nitrogen fertilizer on the incidence of fusarium head blight of wheat with artificial inoculations.A survey conducted in a field trial testing the effect of the plant growth regulator Cerone on the yield components of several cultivars of spring wheat showed that Cerone treatments increased Fusarium infection only in cultivar Columbus. Further research was conducted using cultivar Max, a cultivar susceptible to fusarium head blight, which is widely grown in Quebec. In controlled-condition greenhouse trials, the growth regulators Cycocel and Cerone, as well as nitrogen fertilization did not influence the disease progress. In the 1991 field experiment, the highest incidence of seed infection was observed in Cycocel treatments when the macroconidia of F. graminearum were directly applied to the heads, but not significantly different from the non-treated control. None of the nitrogen levels affect the incidence of seed infection. In the 1992 field trial, the plots were treated with macroconidia of F. graminearum applied to the heads or with Fusarium-colonized corn applied to the rows. Both Cycocel and Cerone significantly increased the incidence of spikelet only in the colonized corn treatments. Cycocel also increased the incidence of seed infection, but only in colonized corn treatments. Cycocel also increased the incidence of seed infection in the non-inoculated treatments. Growth regulators had no effect on the disease when heads were inoculated directly with macroconidia.
48
McCallum, Kevin Reid. „An evaluation of green-waste compost in the growth and yield of wheat“. Thesis, Open University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.392880.
49
Barber, Henry Mark. „Identifying beneficial traits for heat stress around reproductive phases of growth in wheat“. Thesis, University of Reading, 2017. http://centaur.reading.ac.uk/75741/.
Annotation:
There is a need for heat tolerant traits in wheat to be identified in order to maintain and increase yields in future climates. The aim of this project was to assess genotypic variation in crop response to heat stress by comparing a southern European wheat genotype (Renesansa; Rht-D1a, Rht8, Ppd-D1a) with a UK genotype (Savannah; RhtD1b, Ppd-D1b, 1BL/1RS) and their doubled haploid progeny. This would allow for the identification of traits and alleles that would benefit UK and European wheat production under climate change scenarios through the use of a combination of phenotyping, genotyping and crop modelling. Heat stress experiments were conducted in controlled environments to identify the most susceptible growth stages to heat stress within the population and to identify potentially tolerant traits. An appraisal of the crop model SIRIUS and how it simulates heat stress was undertaken. Finally, a field trial was conducted to identify which traits perform well in UK field conditions. Two periods of susceptibility in Savannah and Renesansa were identified as susceptible to heat stress, through reductions in grain number. The first period was identified around booting, with the second being identified one day before mid anthesis. The period around heading was found to be relatively tolerant. Compensation of reduced grain numbers through increases in grain size was limited and variable. Rht8 was not found to influence heat stress tolerance. The photoperiod insensitivity allele Ppd-D1a was found to increase susceptibility to heat stress, while the semi dwarfing allele Rht-D1b was found to confer tolerance to it. Rht8 was associated with reduced yield in UK field conditions. Simulations from SIRIUS suggest that yield loss due to heat stress could increase by three fold in central Europe by 2090, though it is not expected to be a major issue in the UK.
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Mbave, Zwidofhelangani Aubrey. „Water stress effects on growth, yield and quality of wheat (Triticum aestivum L.)“. Diss., University of Pretoria, 2013. http://hdl.handle.net/2263/24146.
Annotation:
Understanding the effects of water stress on wheat growth, yield and quality is essential for good irrigation management. In South Africa most of the wheat production areas are vulnerable to drought stress during crop development. That causes substantial reduction in grain yield, depending on the developmental stage at which water stress occurred. Supplemental irrigation is the main strategy for adaptation and stabilisation of yield under water stress. However, agriculture is the leading single water-use sector locally, consuming about 60% of total available water. Therefore, the need to improve water use efficiency (WUE) in crop production is clear, since South Africa is classified as a water-scarce country. Experiments were conducted under a rain shelter at Hatfield Experimental Farm, University of Pretoria, in the 2010 and 2011 seasons. The main objective of the study was to evaluate the effects of water stress at different stages on growth, yield, and quality of three wheat cultivars, namely Duzi, Steenbras and SST 843. Water stress was imposed by withholding water at either of three growing stages. The first treatment was stressed during tillering stages to flag leaf (stem elongation (SNN)), followed by water stress from flag leaf to the end of flowering (flowering stage (NSN)), and lastly water stress from grain filling to physiological maturing (grain-filling stage (NNS)), whereas optimal supply of water was maintained throughout the season by weekly irrigating to field capacity for the control treatment (NNN). Irrigation treatments and cultivars influenced growth, yield and quality, depending on the developmental stage at which irrigation was withheld. The control treatment (NNN) and the treatment stressed in the flowering stage (NSN) had highest and lowest grain yield respectively in both seasons. Water stressed treatment NSN reduced grain yield by 33% and 35% in the 2010 and 2011 seasons respectively, when compared with the control treatment (NNN). Reduction of grain yield due to stress in the flowering stage (NSN) was ascribed to reduction in the number of seeds per ear, number of ears per unit area, ear length, and flag-leaf photosynthesis rate (Pn). In the flowering stage (NSN) water stress reduced Pn by 59% which was due to increased leaf temperature because of lower transpiration (E) and stomatal conductance (gs). The water stress treatment NSN reduced transpiration by 72% and stomatal conductance by 84% in the flowering stage. Plant height was reduced by 23% because of water stress imposed in the flowering stage (NSN), which consequently decreased biomass yield by 29% in the 2011 season. Growth and yield parameters showed dramatic recovery when stress was terminated during the flag-leaf stage (SNN). The cultivar Steenbras had lower yield reduction under stress, whereas Duzi and SST 843 had higher yield potential under the well-watered conditions (NNN). In the 2011 season SST 843 had higher WUE of 14.2 kg ha-1 mm, which corresponded to higher grain yield of 7210 kg ha-1 and higher ET of 509 mm. Water-stress treatment SNN gave the highest WUE of 14.9 kg ha-1 mm, which corresponded to a total water use (ET) of 451 mm and grain yield of 6738 kg ha-1. Water stress treatments SNN and NNS reduced ET by 27% and 17%, respectively, which translated to 173 mm and 105 mm water saved by each treatment correspondingly. Grain protein content (GPC) was reduced most by the treatment exposed to stress in the stem elongation stage (SNN). However, the GPC was acceptable (>12%) in all treatments in both seasons. Hectolitre mass was reduced most by water stress imposed during grain filling (NNS). Water stress treatment NNS lowered the hectolitre mass by 3% and 4% in the 2010 and 2011 seasons respectively. Generally all quality parameters in the present study were acceptable for all irrigation treatment and cultivars. The hypothesis that water stress in the stem elongation and grain-filling stages will have little effect on yield and improve WUE was accepted. Therefore it can be recommended that supplemental irrigation should be applied from flag leaf to end of flowering (NSN) stages of wheat in order to minimise grain yield losses in the absence of rainfall. Further research should focus on extrapolation of these results to other production regions using crop models.Dissertation (MInstAgrar)--University of Pretoria, 2013.
Plant Production and Soil Science
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