The mitigating effect of cysteine on growth inhibition in salt-stressed barley seeds is related to its own reducing capacity rather than its effects on antioxidant system

Abstract

This research was an attempt to study the effects of exogenous cysteine (Cys) on early seedling growth, amylase activity, enzymatic and non-enzymatic antioxidant systems, reactive oxygen species (ROS), oxidative stress parameters and DNA damage of germinating barley seeds under salt stress (125 mmol l−1 NaCl). Salt stress markedly reduced root elongation and coleoptile growth; these changes could be alleviated by Cys application. Amylase activity exhibited results parallel to early seedling growth. The observed salinity-mediated reduction in amylase activity was markedly impeded by Cys. Isozyme profile confirmed the mitigating effect of Cys on salt-induced amylase inhibition. ROS production was significantly elevated under salt stress. Changes in lipid peroxidation level and DNA damage coincided with high levels of ROS. However, Cys significantly reduced salt-induced ROS production and mitigated oxidative damage to membranes and genetic material. This mitigating effect of Cys was related to low level of ROS as a conclusion its own antioxidant properties rather than its effect on enzymatic and non-enzymatic antioxidants. We found that although Cys application resulted in different effects on antioxidant system in root and coleoptiles, it had partial reducing effect as compared to stressed seedlings in both organs (especially roots). These results were supported by the isozymes activity profiles. Despite the partial reduction determined in antioxidant system in Cys-applied seedlings, low ROS levels revealed that Cys decreases the need for activation of antioxidant system by acting as a ROS scavenger. The evidence from this study suggests that Cys alleviates salt-induced growth inhibition and suppresses oxidative damage in germinating barley seeds by modulating cellular redox status due to its own antioxidant property.