Differential response to sea salt salinity by nitrate and antioxidant system in six soybean varieties

Six varieties of soybean (Glycine max L.) plants were grown for 30 days under three levels of sea salt salinity (0.0, 8.0 and 16.0 mS/cm2) for studying the effect of sea salt on uptake of nitrate and response of the antioxidant system for these salinity doses. Salt treatments resulted in a gradual decline in nitrate uptake by increasing sea salt concentration, which mean that this will bring negative consequences on nitrogen assimilation. However, salt treatments induced the accumulation of hydrogen peroxide and glycinebetaine in the leaves of all soybean verities as an adaptive strategy to cope with salt stress. On the other hand, there was a differential response in phenolic compounds among soybean verities as a function of salt concentration and the studied variety, which means there has a decline in phenolics under salt stress in the varieties Crawford, G21, G22 and G83, but in contrary in G35 and G82, phenolics has accumulated in response to salinity. Isozymes electrophoretic banding showed changes in peroxidase activity with sea salt, however superoxide dismutase showed stability in number and intensity of bands with salt treatments. Esterase enzyme was more sensitive to salinity and showed a gradual decline in activity by increasing salt concentration