Relationship of photosynthetic capacity at the vegetative stage and during grain development with grain yield of two hexaploid wheat (Triticum aestivum L.) cultivars differing in yield

A greenhouse experiment was conducted to draw relationships between rate of photosynthesis and growth at different stages of plant life cycle of two spring wheat cultivars differing in grain yield. Fresh and dry weights of shoots, leaf area per plant, and relative growth rate were higher in Barani-83 than those in Inqlab-91 at the vegetative stage. In contrast, Inqlab-91 was superior to Barani-83 in grain yield per plant, number of grains per spike, and grain weight. The two cultivars differed in CO2 assimilation rate and stomatal conductance during the vegetative growth; Inqlab-91 was superior to Barani-83. In the reproductive phase (from anthesis to grain yield) net CO2 assimilation rate of the flag leaf was the same for the two cultivars. However, cultivars differed significantly only with respect to this variable of second leaf, Inqlab-91 being higher than Barani-83. Both the cultivars used different physiological strategies for grain production. Higher photosynthetic capacity of Inqlab-91 at the vegetative stage seemed to have played a significant role towards its higher grain yield, whereas in contrast, in Barani-83, the higher post-anthesis assimilation rate than that in Inqlab-91 appeared to have played a role in grain yield.