Investigations of water deficit interactions with heat and elevated carbon dioxide in wheat
- Authors: Mavindidze, Peter
- Date: 2021-02
- Subjects: Plants--Effect of heat on , Growth (Plants)
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/20664 , vital:46422
- Description: Future climate is predicted to be characterised by elevated carbon dioxide (eCO2), as well as more incidences of heat and water deficit. eCO2 has been widely reported as enhancing growth, biomass and grain yield. To investigate the interactive effects of abiotic stresses on genotypic performance, an experiment was established in open-top chambers at the University of Rhodes eCO2 facility in Grahamstown, South Africa. The specific objectives of the study were: i) to evaluate the effects of eCO2 on wheat grain yield, yield components and grain quality under heat and terminal water deficit conditions; ii) to identify cultivar sources of tolerance to combined water deficit and heat stress under eCO2; iii) to identify appropriate stress indices that can be used as screening tools for tolerance to combined effects of water deficit and heat stress under eCO2. A total of 19 wheat genotypes were evaluated in three environments varying in CO2, temperature and water deficit during the 2019 winter season. The experiment was laid out in a split-split plot design arranged in blocks inside the chambers. The parameters recorded were: leaf water potential (LWP), biomass content (TB), number of productive tillers (NPT), days to flowering (DTA), days to maturity (DTM), plant height (PH), thousand kernel weight (TKW), number of kernels per spike (KPS), kernel weight per spike (KWS) and total grain weight (TGW). The following stress indices were determined: tolerance index, stress tolerance, yield susceptibility index, mean productivity, geometric mean productivity, stress intensity index and yield index. Elevated atmospheric CO2 ameliorated the negative effects of combined heat and water deficit stress by enhancing LWP, NPT, KPS, TB and TGW. Wheat genotypes responded the same way to CO2 with respect to grain yield. Furthermore, adequate water supply mitigated the adverse effects of heat stress. In addition, the combined effects of eCO2, heat and water deficit are confounding and hypo-additive in nature. The separation of environmental effects revealed that significant genotypic responses on grain yield and biomass were caused by heat and water deficit stress, while eCO2 mitigated their negative effects, promoting growth and reproduction. Both Principal component analysis (PCA) biplot analysis and cultivar superiority measure proved to be reliable statistical tools since they managed to identify 13-5HTSBWYT-H18, Ncema and SST8135 as having both specific adaptations to future climates as well as wide adaption to multiple environments. The genotypes may be used as sources (parents for crosses) for wide adaptation in breeding programmes in the wake of predicted future climate environments. PCA biplot analysis identified mean productivity (MP) and geometric mean productivity (GMP) as the best indices; hence can also be as secondary traits complimenting traditional agronomic and physiological traits in wheat breeding under environments varying in water availability, CO2 and temperature. The interactive effects of eCO2 with heat and water deficit stress did not significantly compromise the grain physical characteristics, flour extraction, protein content, falling number and flour ash. eCO2 ameliorated the negative effects of heat and water deficit by increasing protein content by 4.75 percent , Thesis (MSc) (Crop Science) -- University of Fort Hare, 2021
- Full Text:
- Date Issued: 2021-02
- Authors: Mavindidze, Peter
- Date: 2021-02
- Subjects: Plants--Effect of heat on , Growth (Plants)
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/20664 , vital:46422
- Description: Future climate is predicted to be characterised by elevated carbon dioxide (eCO2), as well as more incidences of heat and water deficit. eCO2 has been widely reported as enhancing growth, biomass and grain yield. To investigate the interactive effects of abiotic stresses on genotypic performance, an experiment was established in open-top chambers at the University of Rhodes eCO2 facility in Grahamstown, South Africa. The specific objectives of the study were: i) to evaluate the effects of eCO2 on wheat grain yield, yield components and grain quality under heat and terminal water deficit conditions; ii) to identify cultivar sources of tolerance to combined water deficit and heat stress under eCO2; iii) to identify appropriate stress indices that can be used as screening tools for tolerance to combined effects of water deficit and heat stress under eCO2. A total of 19 wheat genotypes were evaluated in three environments varying in CO2, temperature and water deficit during the 2019 winter season. The experiment was laid out in a split-split plot design arranged in blocks inside the chambers. The parameters recorded were: leaf water potential (LWP), biomass content (TB), number of productive tillers (NPT), days to flowering (DTA), days to maturity (DTM), plant height (PH), thousand kernel weight (TKW), number of kernels per spike (KPS), kernel weight per spike (KWS) and total grain weight (TGW). The following stress indices were determined: tolerance index, stress tolerance, yield susceptibility index, mean productivity, geometric mean productivity, stress intensity index and yield index. Elevated atmospheric CO2 ameliorated the negative effects of combined heat and water deficit stress by enhancing LWP, NPT, KPS, TB and TGW. Wheat genotypes responded the same way to CO2 with respect to grain yield. Furthermore, adequate water supply mitigated the adverse effects of heat stress. In addition, the combined effects of eCO2, heat and water deficit are confounding and hypo-additive in nature. The separation of environmental effects revealed that significant genotypic responses on grain yield and biomass were caused by heat and water deficit stress, while eCO2 mitigated their negative effects, promoting growth and reproduction. Both Principal component analysis (PCA) biplot analysis and cultivar superiority measure proved to be reliable statistical tools since they managed to identify 13-5HTSBWYT-H18, Ncema and SST8135 as having both specific adaptations to future climates as well as wide adaption to multiple environments. The genotypes may be used as sources (parents for crosses) for wide adaptation in breeding programmes in the wake of predicted future climate environments. PCA biplot analysis identified mean productivity (MP) and geometric mean productivity (GMP) as the best indices; hence can also be as secondary traits complimenting traditional agronomic and physiological traits in wheat breeding under environments varying in water availability, CO2 and temperature. The interactive effects of eCO2 with heat and water deficit stress did not significantly compromise the grain physical characteristics, flour extraction, protein content, falling number and flour ash. eCO2 ameliorated the negative effects of heat and water deficit by increasing protein content by 4.75 percent , Thesis (MSc) (Crop Science) -- University of Fort Hare, 2021
- Full Text:
- Date Issued: 2021-02
Photosynthetic and growth response of C₃ and C₄ subspecies of Alloteropsis semialata to nitrogen-supply
- Authors: Abraham, Trevor Ian
- Date: 2008
- Subjects: Photosynthesis , Plants -- Effect of nitrogen on , Growth (Plants) , Plant ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4182 , http://hdl.handle.net/10962/d1003750 , Photosynthesis , Plants -- Effect of nitrogen on , Growth (Plants) , Plant ecology
- Description: The greater photosynthetic nitrogen use efficiency (PNUE) of C4 compared with C3 plants may explain the relative success of C4 grasses in nutrient poor environments. This study compared the responses in photosynthetic parameters, leaf nitrogen and biomass allocation between the C3 and C4 subspecies of Alloteropsis semialata supplied soil nitrogen at three levels. Photosynthesis was assessed by means of CO2 response curves and the leaf nitrogen content assayed. Plants were destructively harvested, leaf areas determined and the dry biomass of functional plant components was measured. Results confirmed that the higher PNUE of C4 plants allowed them to accumulate more biomass than C3 plants at the high nitrogen level, despite smaller leaf areas. The greater productivity of C4 plants enabled them to invest more in storage and sexual reproduction than in leaves when compared to the C3 plants. In contrast the C3 plants invested biomass in less efficient and more nitrogen demanding leaves and bigger root systems. PNUE and photosynthetic rates were not significantly affected by nitrogen-limitation in either subspecies and the major response was a decrease in biomass accumulation and an increase in biomass allocation to roots. This altered root to shoot ratio was accompanied by a lowered allocation to sexual reproduction in the C4 subspecies, but an unaltered allocation to leaves, while in the C3 subspecies there was a decrease in leaf allocation. In a further experiment, the C4 subspecies was supplied three levels of nitrogen provided as nitrate, or alternatively as ammonium plus nitrate, and leaves were excised to within 5 cm of the ground at the start of treatment. Prior to flowering, photosynthesis was assessed by means of CO2 response curves and the plants were destructively harvested. Leaf areas and the dry biomass of functional plant components were determined, and at levels of nitrogen supply higher than those found in savanna soils the rate of photosynthesis was increased. Leaf re-growth was reduced by severe nitrogen limitation and co-provision of nitrate and ammonium had no significant effect other than increased tillering. Both subspecies of Alloteropsis semialata are adapted to nutrient poor environments and maintain photosynthetic rates by reducing leaf area. The C4 subspecies is likely to show greater resilience in disturbance-prone environments by exploiting its higher PNUE to allocate greater resources to storage and sexual reproduction, while the C3 subspecies is usually found in environments with closed canopies which favour vegetative growth, and allocate greater resources to leaves and roots.
- Full Text:
- Date Issued: 2008
- Authors: Abraham, Trevor Ian
- Date: 2008
- Subjects: Photosynthesis , Plants -- Effect of nitrogen on , Growth (Plants) , Plant ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4182 , http://hdl.handle.net/10962/d1003750 , Photosynthesis , Plants -- Effect of nitrogen on , Growth (Plants) , Plant ecology
- Description: The greater photosynthetic nitrogen use efficiency (PNUE) of C4 compared with C3 plants may explain the relative success of C4 grasses in nutrient poor environments. This study compared the responses in photosynthetic parameters, leaf nitrogen and biomass allocation between the C3 and C4 subspecies of Alloteropsis semialata supplied soil nitrogen at three levels. Photosynthesis was assessed by means of CO2 response curves and the leaf nitrogen content assayed. Plants were destructively harvested, leaf areas determined and the dry biomass of functional plant components was measured. Results confirmed that the higher PNUE of C4 plants allowed them to accumulate more biomass than C3 plants at the high nitrogen level, despite smaller leaf areas. The greater productivity of C4 plants enabled them to invest more in storage and sexual reproduction than in leaves when compared to the C3 plants. In contrast the C3 plants invested biomass in less efficient and more nitrogen demanding leaves and bigger root systems. PNUE and photosynthetic rates were not significantly affected by nitrogen-limitation in either subspecies and the major response was a decrease in biomass accumulation and an increase in biomass allocation to roots. This altered root to shoot ratio was accompanied by a lowered allocation to sexual reproduction in the C4 subspecies, but an unaltered allocation to leaves, while in the C3 subspecies there was a decrease in leaf allocation. In a further experiment, the C4 subspecies was supplied three levels of nitrogen provided as nitrate, or alternatively as ammonium plus nitrate, and leaves were excised to within 5 cm of the ground at the start of treatment. Prior to flowering, photosynthesis was assessed by means of CO2 response curves and the plants were destructively harvested. Leaf areas and the dry biomass of functional plant components were determined, and at levels of nitrogen supply higher than those found in savanna soils the rate of photosynthesis was increased. Leaf re-growth was reduced by severe nitrogen limitation and co-provision of nitrate and ammonium had no significant effect other than increased tillering. Both subspecies of Alloteropsis semialata are adapted to nutrient poor environments and maintain photosynthetic rates by reducing leaf area. The C4 subspecies is likely to show greater resilience in disturbance-prone environments by exploiting its higher PNUE to allocate greater resources to storage and sexual reproduction, while the C3 subspecies is usually found in environments with closed canopies which favour vegetative growth, and allocate greater resources to leaves and roots.
- Full Text:
- Date Issued: 2008
A study of the distribution of nutrients during the growth of cayenne pineapples under field conditions
- Authors: Fowler, William Mackenzie
- Date: 1977
- Subjects: Plants -- Nutrition , Pineapple -- Crop yields , Growth (Plants) , Field Crops -- Nutrition
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4260 , http://hdl.handle.net/10962/d1011888 , Plants -- Nutrition , Pineapple -- Crop yields , Growth (Plants) , Field Crops -- Nutrition
- Description: The purpose of this study was to determine the uptake and distribution of nutrients during the growth of the Cayenne cultivar of Ananas comosus (L) Merr under field conditions in the Eastern Cape. The study was also done to help explain the apparent drop in the nutrient levels in the basal section of the "D"- leaf of the pineapple plant during the winter months and to determine the best part or parts of the plant to sample in order to measure the nutrient status of the pineapple plant at any stage of its growth. The investigation was conducted by selecting a plot within a production land on two farms in the pineapple growing region of the Eastern Cape. Plants were sampled from each plot at regular intervals from planting of the pineapple tops until the harvesting of the fruit of the first plant crop. Plant growth was measured and the nutrient concentrations in each section of the plant were determined. The total amounts of nutrients for each plant part were calculated and the nutrient uptake was compared and plotted on distribution diagrams.
- Full Text:
- Date Issued: 1977
- Authors: Fowler, William Mackenzie
- Date: 1977
- Subjects: Plants -- Nutrition , Pineapple -- Crop yields , Growth (Plants) , Field Crops -- Nutrition
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4260 , http://hdl.handle.net/10962/d1011888 , Plants -- Nutrition , Pineapple -- Crop yields , Growth (Plants) , Field Crops -- Nutrition
- Description: The purpose of this study was to determine the uptake and distribution of nutrients during the growth of the Cayenne cultivar of Ananas comosus (L) Merr under field conditions in the Eastern Cape. The study was also done to help explain the apparent drop in the nutrient levels in the basal section of the "D"- leaf of the pineapple plant during the winter months and to determine the best part or parts of the plant to sample in order to measure the nutrient status of the pineapple plant at any stage of its growth. The investigation was conducted by selecting a plot within a production land on two farms in the pineapple growing region of the Eastern Cape. Plants were sampled from each plot at regular intervals from planting of the pineapple tops until the harvesting of the fruit of the first plant crop. Plant growth was measured and the nutrient concentrations in each section of the plant were determined. The total amounts of nutrients for each plant part were calculated and the nutrient uptake was compared and plotted on distribution diagrams.
- Full Text:
- Date Issued: 1977
The effect of different levels and intervals of application of ammonium sulphate on the growth, chemical composition and yield of cayenne and queen pineapple plants under field conditions
- Van Lelyveld, Louis Johannes
- Authors: Van Lelyveld, Louis Johannes
- Date: 1965
- Subjects: Pineapple -- Crop yields , Plants -- Nutrition -- South Africa , Growth (Plants) , Nitrogen fertilizers , Field Crops -- Nutrition , Ammonium sulfate
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4263 , http://hdl.handle.net/10962/d1013422
- Description: From the Introduction. The fertilisation of pineapples in the Eastern Cape Province is still a relatively new practice which started approximately twelve years ago. Even after this time many growers still insist that pineapples can be grown without fertilisation on virgin soils. As the available virgin soil decreased, however, so the interest in fertiliser application increased. Very little basic research on the fertiliser requirements of pineapples in the Eastern Cape was done to serve as a guide to growers. The available advisory literature by le Roux (1951), Malan (1954) and Lewcock (1956) were based on overseas experience. When pineapple research was started on a large scale, in 1955, it was realised that emphasis should be placed on the nutritional requirements on virgin as well as replanted soils. From initial experiments it was clear that the main response in plant growth and yield was obtained from nitrogenous fertilisers.
- Full Text:
- Date Issued: 1965
- Authors: Van Lelyveld, Louis Johannes
- Date: 1965
- Subjects: Pineapple -- Crop yields , Plants -- Nutrition -- South Africa , Growth (Plants) , Nitrogen fertilizers , Field Crops -- Nutrition , Ammonium sulfate
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4263 , http://hdl.handle.net/10962/d1013422
- Description: From the Introduction. The fertilisation of pineapples in the Eastern Cape Province is still a relatively new practice which started approximately twelve years ago. Even after this time many growers still insist that pineapples can be grown without fertilisation on virgin soils. As the available virgin soil decreased, however, so the interest in fertiliser application increased. Very little basic research on the fertiliser requirements of pineapples in the Eastern Cape was done to serve as a guide to growers. The available advisory literature by le Roux (1951), Malan (1954) and Lewcock (1956) were based on overseas experience. When pineapple research was started on a large scale, in 1955, it was realised that emphasis should be placed on the nutritional requirements on virgin as well as replanted soils. From initial experiments it was clear that the main response in plant growth and yield was obtained from nitrogenous fertilisers.
- Full Text:
- Date Issued: 1965
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