Physiological and biochemical response of different soybean cultivars under water deficit tension in vegetative and reproductive growth stages

Considering the importance of soybean and the effect of water deficit in arid and semi-arid regions on the reduction of the plant yield, this research was carried out in order to investigate the physiological and biochemical responses of different soybeans cultivars in the face of water deficit tension in different stages of vegetative and reproductive growth. A factorial experiment was conducted in a randomized complete blocks design with four replications at the Agricultural and Natural Resources Campus of Razi University of Kermanshah in 2012-2013. The investigated treatments were included: water regime (1-control, 2- water deficit tension from vegetative stage and 3-water deficit tension from reproductive stage until maturity) and different soybean cultivars (including: Williams, L17, M9, M7 and Zan). The results indicated that application of water deficit tension at vegetative and reproductive stage of growth with the exception of M7 cultivar, compared to control treatment, had a significant effect on grain yield of other cultivars. The highest reduction in grain yield at both levels of water deficit tension was related to Williams cultivar with 57 and 51 percent reduction, respectively. Application of water deficit tension at vegetative and reproductive stage of growth significantly reduced the content of chlorophyll a and b pigments, maximum photochemical efficiency of photosystem II, soluble proteins and relative water content of leaf and increased carotenoids, soluble sugars and proline content and stomatal resistance value and activity rate of antioxidant enzymes catalase, peroxidase and superoxide dismutase of leaves. Among the investigated traits, stomatal resistance value and proline content of leaves under water deficit tension conditions had the highest increase compared to control conditions. Among the antioxidant enzymes, peroxidase had the highest rate of activity in both moisture conditions in the investigated cultivars.