Biochemical responses of sorghum cultivars under salinity at vegetative and reproductive stages

An experiment was conducted to study the effects of salinity (control, 50, 100, 150, and 200 mM NaCl) on antioxidants and osmolytes in Kimia (grain) and Pegah (sweet-forage) cultivars of sorghum at vegetative and reproductive stages. There were significant differences for potassium/sodium ratio and relative water content (RWC) at vegetative and reproductive stages, as the values were higher at vegetative stage, while leaf stomatal conductance (gs), lipid peroxidation in terms of malondialdehyde content, hydrogen peroxide content, antioxidants and osmolytes were higher at reproductive stage. Salinity enhanced leaf antioxidative defense and decreased leaf K+/Na+ ratio and cell membrane stability at both stages. However, the changes were greater at the highest saline level at vegetative stage. Although RWC and gs were not influenced by salinity at vegetative stage, they significantly decreased at reproductive stage. Further, the sweet-forage cultivar was more salt-tolerant than the grain cultivar at both the stages. It seemed that assaying oxidative and antioxidative characteristics of leaves at different phenological stages could assist in evaluating cultivars’ tolerance to salinity.