Acclimation of hydrogen peroxide enhances salt tolerance by activating defense-related proteins in Panax ginseng C.A. Meyer

The effect of exogenously applied hydrogen peroxide on salt stress tolerance was investigated in Panax ginseng. Pretreatment of ginseng seedlings with 100 μM H₂O₂ increased the physiological salt tolerance of the ginseng plant and was used as the optimum concentration to induce salt tolerance capacity. Treatment with exogenous H₂O₂ for 2 days significantly enhanced salt stress tolerance in ginseng seedlings by increasing the activities of ascorbate peroxidase, catalase and guaiacol peroxidase and by decreasing the concentrations of malondialdehyde (MDA) and endogenous H₂O₂ as well as the production rate of superoxide radical (O₂ ^?). There was a positive physiological effect on the growth and development of salt-stressed seedlings by exogenous H₂O₂ as measured by ginseng dry weight and both chlorophyll and carotenoid contents. Exogenous H₂O₂ induced changes in MDA, O₂ ^?, antioxidant enzymes and antioxidant compounds, which are responsible for increases in salt stress tolerance. Salt treatment caused drastic declines in ginseng growth and antioxidants levels; whereas, acclimation treatment with H₂O₂ allowed the ginseng seedlings to recover from salt stress by up-regulation of defense-related proteins such as antioxidant enzymes and antioxidant compounds.