Relationship between Growth and Photosynthetic Efficiency of Soybean (Glycine max L. Merrill) Genotypes under variable Photoperiods

Relationship between Growth and Photosynthetic Efficiency of Soybean (Glycine max L. Merrill) Genotypes under variable Photoperiods

Photosynthetic rate and leaf area index are the most important traits for determining the yield of soybean. LAI, photosynthetic rate and growth efficiency during the different growth and developmental stages of soybean were strongly influenced by variable photoperiods. The objective was to investigate the alteration of source-sink of different maturity group soybean genotypes under variable photoperiods (longer and shorter) and to examine the dynamics of LAI, photosynthetic rate and growth efficiency (CGR and RGR) at the different growth and development stages. Fifteen soybean genotypes of three maturity groups were grown under variable photoperiods at Punjab Agricultural University, Ludhiana, India in a Randomized Block Design along with three replications. LAI and photosynthetic rate were recorded at vegetative, flowering and pod initiation stages of each photoperiod. Growth efficiency was measured at two intervals i.e. 30-45 DAS and 45-60 DAS. Significant variations were found for LAI, photosynthetic rate, growth efficiency, duration from R1 to R8 period and yield contributing traits within each maturity groups. Late maturity group genotypes had higher LAI, Photosynthetic rate, CGR, RGR and yield attributes traits than medium and early ones under both the photoperiodic conditions. A strong positive relation was found for LAI, photosynthetic rate and crop growth rate with grain yield per plant in late maturity group genotypes. The confirmation obtained in the present studies further proved that photoperiods influence the whole life cycle of soybean crop.