Comparative morphological and physiological responses of green gram genotypes to salinity applied at different growth stages

Experiments were conducted to find the difference among green gram (Vigna radiata L. Wilczek) genotypes for salinity tolerance during germination and during vegetative and reproductive growth stages under NaCl treatment. Data revealed significant genotypic differences in germination percentage and post-germination survival of seedlings, symptoms of salt injury, changes in the levels of Na+, Cl- and K+ and total chlorophyll at the vegetative stage, and in pod development, seed yield, and yield components at the reproductive stage. Salinity tolerance in green gram was related to greater final germination and post-germination seedling survival, low scorching, chlorosis and necrosis of aerial parts, reduced Na+ and Cl-, slightly enhanced K+, and greater chlorophyll content. Appearance of increased symptoms on the aerial parts was positively related to increased Na+ and Cl- and negatively to increased K+. At maturity, pod weight, seed:hull weight ratio, 100-seed weight, seed yield and harvest index were also greater in M-6601. Maintenance of a steady seed:hull weight ratio in M-6601 indicated that a higher seed yield in this genotype is principally due to a greater partitioning of photoassimilates to seed rather than hull during pod development under saline conditions. Based on these criteria, M-6601 and 241/11 were declared salt tolerant and sensitive, respectively. Essentially then, ion-toxicity is the dominant factor modulating the salt tolerance of green gram during growth periods,