Abstract:

A hydroponic experiment was conducted to study the effects of CaCl2 on the ascorbate- glutathione（AsA-GSH）cycle in roots，stems，and leaves of sour jujube（Ziziphus acidojujuba C. Y. Cheng et M. J. Liu）under NaCl stress. The results showed that NaCl stress significantly increased the absocrbic acid（AsA）content and monodehydroascorbate reductase（MDHAR）activity in sour jujube roots and leaves. In contrast，NaCl stress reduced the ascorbate peroxidase（APX）activity in those organs. Glutathione（GSH）content in roots，stems，and leaves were significantly greater in the NaCl treatment than in the control treatment. The addition of CaCl2 to the hydroponic solution increased AsA content in shoots and stems compared with the NaCl treatment. In contrast，NaCl + CaCl2 reduced AsA concentrations and APX activity in leaves. The NaCl + CaCl2 treatment also significantly increased MDHAR activity in roots and DHAR activity in leaves and stem. The GSH content in roots and leaves was less in the NaCl + CaCl2 treatment than in the NaCl treatment. In conclusion，exogenous CaCl2 improved AsA regeneration in sour jujube roots and stems by increasing the MDHAR and DHAR activities in roots，stems，and leaves. The CaCl2 also promoted AsA synthesis in sour jujube stems and roots. The CaCl2 improved the ability of sour jujube seedlings under NaCl stress to eliminate hydrogen peroxide（H2O2）by increasing AsA content in roots and stems.

Key words: sour jujube, CaCl2, NaCl stress, AsA-GSH cycle