Photoperiodic Dynamics alters biomass accumulation and its Partitioning in Soybean (Glycine max. L. Merrill) Genotypes Under Sub-Tropical Punjab Conditions

Soybean is a quantitative short-day plant and is very sensitive to photoperiod that is the reason it does not change from vegetative to reproductive growth until a critical day length is met. Our objective was investigation of photoperiodic changes effect on important physiological traits such as dry matter production and harvest index that affected grain yield. A field experiment was carried out in randomized block design with three replications. Fifteen divergent genotypes of soybean (Glycine max. L. Merrill) were grouped into three categories on the basis of maturity dates; early, medium and late were planted on two planting dates (normal and late). Grain yield increased with increasing biomass and its proper utilization under optimal planting date and decreased with delaying in planting date due to improper accumulation of photosynthate between vegetative to reproductive phase. Compared with the normal sowing, the delayed sowing genotypes had the lower dry matter which indicated that the photoperiodic changes would affect the duration of growth under different sowing dates. Finally, the results depicted that in early (EC 457161), medium, (SL 983) and late (SL 958) maturity date genotypes produce maximum dry matter accumulation and gave higher yield in normal sowing due to better environmental conditions as compared to late sown conditions.