Physiological effects of water deficit stress on seed yield, antioxidants activities and lipid peroxidation in soybean cultivars (Glycine max)

In the water deficit stress, free radicals of oxygen increase that can be harmful because of its oxidative and destructive effects on the metabolism of plants. Therefore, field experiments were conducted in 2008-2009- and 2009-2010 to determine the effect of water deficit on the agronomical, physiological and biochemical properties of soybean cultivars. The experimental design was randomized complete block in a split plot arrangement with four replications. Irrigation treatments were (S1, 50; S2, 100 and S3, 150 mm evaporation from the Class “A pan” evaporation) and cultivars were (L17, Clean, T.M.S, Williams×Chippewa and M9). Results showed that, water deficit stress increased antioxidant activities (SOD and GPX), ABA content and lipid peroxidation (MDA content). Of course, the content of antioxidant enzymes were more at moderate than extreme water deficit (S2>S3>S1). Furthermore, Water deficit decreased number of pods per plant, total dry weight (TDW) and seed yield in all of cultivars. Among cultivars, L17 and Williams×Chippewa produced the highest seed yield at the optimum condition of irrigation and both water deficit stress levels, respectively. Assessment of correlation results indicated that, there was a positive and significant correlation among SOD and ABA content with seed yield in both water deficit stress levels, too.