Physiological analysis of yield variation in gram (Cicer arietinum L.) genotypes

Nine genotypes of gram (Cicer arietinum L.) were evaluated for their net assimilation rate (NAR), crop growth rate (CGR) relative growth rate (RGR) and photosynthetic ¹⁴CO₂ fixation rate, and per cent transmission of photosynthetically active rediation (PAR 400-700 nm) in the canopy. CGR and RGR were low in the beginning and rose to peak at 85-91 days after planting (DAP) and then declined slowly in most of the varieties. The increase in CGR during reproductive phase was accompanied by concurrent increase in NAR. Genotypic differences for NAR were significant in the period from 85 to 119 DAP. Only three varieties, viz. C235, G130 and JG-36 showed an increase in NAR upto 113-119 days after sowing. The increase in NAR during reproductive phase was interpreted as a response of the photosynthetic apparatus to an increased demand for assimilates in the rapidly growing seed fraction. At all stages of growth, correlation of CGR with grain yield was positive but was significant only during pod development. The RGR in the period during pod development was significantly associated with grain yield. Per cent transmission of PAR was minimum in Plant 104, H-214, H-208 and K₄ which gave highest grain yield except K₄. PAR transmission was highly correlated with grain yield at early pod filling stage (r=0.67). The rate of ¹⁴CO₂ fixation was maximum in Pant-104 and lowest in JG-35. The extent of variation in rate of photsynthesis was found from 100 to 171 per cent