The response of wildtype and mutant cultivars of soybean to salt stress - comparing vegetative and reproductive phases on the basis of leaf biochemical contents, RWC, and stomatal conductance

Soybean, as a major oilseed crop, is cultivated in many parts of the world including saline-affected regions. A four-replicated factorial experiment based on a completely randomized design with five salinity levels (control, 50, 100, 150, and 200 mM NaCl) and five wild-type and new mutant cultivars of soybean (Williams, Clark, M-4, M-7, and M-9) was done at two vegetative and reproductive phases to study leaf oxidants, antioxidants and osmolytes under salinity stress. The vegetative phase demonstrated higher K⁺:Na⁺ ratio, cell membrane stability, relative water content (RWC) and stomatal conductance to H₂O (gs) accompanied with lower oxidative stress, antioxidants and osmolytes contrasting to reproductive phase. At both phenological phases, saline stress stimulated antioxidative defense owing to the enhancement of oxidative stress. The results indicated that mutants possessed a better antioxidative system than their wild-types.