42 Figure 5.5: Plant height of two pea varieties (brown mix and white birch) grown under water stress. 42 Figure 5.6: Plant height of two pea varieties (brown mix and white birch) in response to change.
Introduction
Global agricultural production is often limited by environmental factors such as temperature and water stress. This will also help to characterize the crop for water stress, as the physiology of the crop is related to drought stress.
Aims and Objectives
In response to recurrent drought in South Africa, detailed research of the cowpea's physiological responses to water stress is important to help farmers improve its yield and overcome production limitations, as crop physiological changes are the result of crop response to the environment. The crop has the potential to provide food to the ever-increasing human population in developing countries.
LITERATURE REVIEW
- Cowpea
- Classification
- Origin and domestication
- Plant morphology
- Genetic diversity
- Ecology
- World production of cowpea
- Uses and importance
- Agronomy
- Cultural practices
- Fertilization
- Irrigation
- Pests and diseases
- Weed control
- Harvesting
- Storage
- Drought Tolerance and Water Use
- Drought effect
- Water use
- Adaptation mechanism to water stress
- Chlorophyll content
- Proline accumulation
- Protein synthesis and accumulation
- Seed Quality
- Conclusion
Poor weed control or delay in weeding causes drastic reduction in yield (Dugje et al. 2009). Drought is a major environmental stress that affects plant growth and development (Harb et al. 2010).
MATERIALS AND METHODS
- Plant Materials
- Seed Quality Tests
- Tetrazolium test (TZ)
- Standard Germination (SG) test
- Electrolyte leakage test (EC)
- Controlled Environment Study
- Controlled environment conditions
- Experimental design, potting procedure, water stress treatments
- Soil characteristics
- Crop management
- Data collection
- Field Experiments
- Experimental site description
- Weather and soil water content
- Experimental design, irrigation and planting
- Crop management
- Data collection
- Description of Statistical Analyses
Leaf chlorophyll content was measured weekly using a chlorophyll content meter (CCM-200 Plus, Opti–Sciences, USA). Plant height was also measured weekly using a meter ruler starting from the soil surface up to the base of an uppermost leaf.
SEED QUALITY COMPONENTS OF COWPEA VARIETIES BROWN MIX AND
- Introduction
- Results
- Tetrazolium test
- Standard germination test
- Electrolyte leakage
- Discussion
- Conclusion
As such, the results indicated that the White Birch variety was more vigorous than the Brown Mix variety. The Brown mixture variety was more viable (germinated better and all seeds were normally colored red) compared to White birch.
EFFECTS OF WATER STRESS ON PHYSIOLOGY, GROWTH AND YIELD OF
Introduction
Many aspects of plant growth are also affected by drought stress, these include plant height, leaf number and leaf expansion, stem elongation and leaf area index (Loka et al. 2011)). Water stress remains a constraint to crop production in semi-arid and semi-arid areas where cowpea is mainly grown (Akyempong 1986). Drier climates are predicted due to ongoing climate change and variability; cowpea is one of the crops that can contribute to future food security in semi-arid regions.
Although the effects of water stress on pea production have been studied, little is known about the effects of water stress on physiological mechanisms, growth and yield components. A better understanding of the effects of water stress on pea growth and physiology will provide farmers with useful information on how to manage pea production under different environmental conditions. Therefore, the objective of this study was to evaluate the effect of water stress on physiological changes, growth, yield and yield components of two pea varieties (brown mix and white birch) grown under different water regimes under controlled environmental conditions. .
Results
- Soil water content
- Physiological parameters
- Growth parameters
- Flowering
- Yield components
- Seed quality tests
- Proline and protein analysis
There was no significant interaction (P > 0.05) between water regimes and cultivars over time with respect to plant height (Figures 5.4, 5.5 and 5.6). There were highly significant differences (P < 0.001) between water regimes for number of pods per plant (Table 5.1). Regarding the number of seeds per pods, no significant differences (P > 0.05) were observed between cultivars and between water regimes.
Similar to pod number per plant, the interaction between water regimes and varieties was not significant. Results of the standard germination test showed significant differences (P < 0.05) between the two varieties (Figure 5.10). Results of germination vigor indices (root length, shoot length, root:shoot ratio) of the two varieties showed no significant differences (P > 0.05) between water regimes (Table 5.2).
Mean time to germination (MGT) and germination velocity index (GVI) showed no significant differences (P > 0.05) between varieties and between water regimes (Table 5.2). Electrical conductivity results showed no significant differences (P . > 0.05) between the two pea varieties under different water regimes.
Discussion
Previous studies on other buttercups (Anjum et al. 2010; Mabhaudhi and Modi 2013) also reported reduction in plant height due to water deficit. The reduction in plant height under water stress was attributed to inhibition of cell division and proliferation under water stress (Manivannan et al. 2007). The results of this study showed that leaf number was significantly affected by water stress at 60% and 30% ETc.
Previous studies showed reduction in leaf number due to water stress (Mbatha and Modi 2010; . Ntombela 2013). White birch had more pods compared to brown mixture; this may indicate better adaptation to water stress in white birch compared to brown mixture. The results obtained showed that seed quality (viability and vigor) did not decrease in relation to water stress.
Chlorophyll content index is not a sensitive parameter for water stress but can be useful in predicting crop maturity. The Witberk variety was better adapted to water stress and produced a good harvest index compared to Bruinmix.
EFFECTS OF PLANTING DATES ON PHYSIOLOGY, GROWTH AND YIELD
Introduction
In western Colorado, for example, corn planting date selection ensures physiological maturity before fall frost (Anapalli et al. 2005). It was revealed by Mbong et al. 2010), who reported that early-sown cowpeas had higher incidence of scab infection compared to late-sown cowpeas. An appropriate planting date of a crop is defined as a date when the plants can establish well and their susceptible growth stages do not coincide with unfavorable environmental conditions (Seghatoleslami et al. 2013).
The work done by Wilson et al. 2012) in pigeon pea also showed higher stomatal conductance in late planted plots compared to earlier planted ones. According to Sidibe et al. 1996), soybean seed quality was improved by delaying the planting date. In peas, good yield has been reported to be obtained by determining the onset and duration of rainfall (Dugje et al. 2009).
Other criteria also considered for planting dates include; temperature, precipitation distribution and the maturity period of the varieties used (Tayebi et al. 2012; Sadeghi and Niyaki 2013). To date, significant progress has been made in determining the effect of planting dates on cowpea (Mbong et al. 2010; Peksen et al. 2002).
Result
- Weather data
- Soil water content
- Emergence
- Physiological Parameters
- Stomatal conductance
- Chlorophyll Content Index (CCI)
- Growth Parameters
- Leaf number
- Plant height
- Flowering
- Yield components
- Biomass
- Pod number per plant
- Seed number per pod
- Seed mass per pod
- Seed weight per plant (Yield)
- Seed quality test (viability and moisture content)
- Seed viability
- Seed moisture content
There were no significant differences (P>0.05) between the two varieties regarding emergence time. The interaction between variety and planting date was not significant (P>0.05) in relation to yield. For all planting dates, there were no significant differences (P>0.05) between water regimes, except for the third planting.
No significant differences (P>0.05) were observed between the two varieties for rain-fed and irrigated plots, during all three plantings. No significant difference (P>0.05) was found between the water regimes, regarding the number of pods per plant. A significant difference (P<0.05) was observed between the two water regimes, with regard to germination (Figure 6.16).
No significant differences (P>0.05) were found between the two cowpea species under either rain-fed or irrigated plots. No significant difference (P>0.05) was found between the two varieties (Brown Mix and White Birch) in seed moisture content.
Discussion
White birch variety emerged early compared to Brown mix, especially on the second and third planting dates. Results obtained are consistent with seed quality test results observed in this experiment (chapter 4), which showed more vigor in White Birch variety compared to Brown mixture. Emergence results were similar to the day-to-emergence results observed in the present experiment, which also indicated more vigor in White Birch variety compared to Brown Mix variety.
The variety Brown mixture had a higher chlorophyll content in all three planting dates compared to the variety White birch. On the other hand, the higher biomass found in white birch in the third planting date compared to the brown mixture may be due to more pods (without seeds) per plant observed in white birch compared to the brown mixture. This could be attributed to the greater number of leaves and plant height observed in the white birch compared to the brown mixture (Figures 6.7 and 6.8).
White birch producing more seeds per pod compared to the brown mix may indicate greater adaptation to environmental conditions. The higher seed weight per plant observed in White Birch compared to Brown Mix can be attributed to a higher number of pods.
Conclusion
Although no significant difference was found between the two water regimes; However, irrigated plants had the highest seed moisture compared to non-irrigated plants (Figure 6.12). These results are consistent with previous report, which indicated that the moisture content of snap beans grown under the conditions of optimal irrigation was higher than those deprived of irrigation (Eskin 1989).
GENERAL DISCUSSION
Introduction
Planting date management is one of the management practices used by farmers to cope with limited water resources (low rainfall, soil water content and water availability) in arid and semi-arid regions.
Aim and objectives
Challenges
Future Teaching, Learning and Research Possibilities
In the current study, only two species of cowpea were used; future research should include more varieties to allow effective assessment of water stress on cowpea physiology. Future research should include more physiological (leaf water potential, chlorophyll fluorescence) and growth parameters (branch number, Leaf Area Index), to obtain more data on the physiological responses of crops to water stress. Leaves of the brown mix variety were found to contain more chlorophyll than white birch.
However, future study should evaluate the biological basis for the relationship between leaf chlorophyll content and variety. The interval between planting dates used in the present experiment was two months; It is also recommended that future studies reduce these intervals in order to have a broad knowledge of the effects of planting date on chickpea physiology.
Final Comments and Summary Conclusions
Effect of water stress applied at different growth stages on seed yield and water use efficiency in pea. Effect of water stress on yield of Vigna unguiculata pea genotypes in the Delmarva regions of the United States. 2007. Effect of water stress at different growth stages on components and grain yield of common bean (Phaseolus vulgaris L.) African Crop Science Proceedings.
Effect of water stress at different stages on components and grain yield in common bean (Phaseolus vulgaris). Effects of water stress on rooting, nodulation potential and growth of cowpea (Vigna unguiculata (L.) Walp). Effect of water stress at different developmental stages on the vegetative and reproductive growth of maize.
