Physiological basis of yield differences between two bean (phaseolus vulgaris) varieties
A study was carried out to investigate physiological basis of yield differences between two bean varieties namely GLP-I004 .and GLP-2. Single leaf net photosynthetic rate per unit area, leaf nitrogen content, soluble carbohydrates content of stems and leaves, biomass accumulation and final seed yield were monitored. Results showed that GLP-I004 had a higher single leaf net photosynthetic rate per unit area than GLP-2. It also had a higher rate of leaf area development and biomass accumulation. There was no significant difference in chlorophyll content between the two varieties in pot experiment whereas in field experiment GLP-I004 had significantly higher chlorophyll content 38 DAE to 52 DAE. GLP-I004 had significantly higher leaf nitrogen content than GLP-2 in pot experiment but in field experiment significant difference was observed at 45 DAE. GLP-I004 also had significantly higher amounts of soluble carbohydrates namely glucose, fructose and sucrose in its vegetative parts than GLP-2 in both experiments. GLP-I004 had more pods per plant and seeds per pod and it outyielded GLP-2. It is suggested that single leaf net photosynthetic rate may be indicative of yield differences among bean cultivars although varietal differences in light reactions (as measured by chlorophyll content) and carbon reduction pathway (measured by N content) were not consistent between the glass house and field experiments. Soluble sugar content of the vegetative parts appears even more consistent as indicator of yield. It is reccomended that more bean varieties be used to further evaluate the selective value of these parameters.