Exogenous CaCl2 reduces salt stress in sour jujube by reducing Na+ and increasing K+, Ca2+, and Mg2+ in different plant organs

In this study, we investigated the effects of 10 mM CaCl2 on membrane permeability, malondialdehyde (MDA), reactive oxygen species (ROS), and Na+, K+, Ca2+, and Mg2+ concentrations in different organs of sour jujube grown under 150 mM NaCl stress. Our results showed 73% leaf wilting in the Na treatment. The Na treatment significantly increased leaf superoxide (O-2(.-)) production rates, hydrogen peroxide (H2O2) concentrations, cell membrane permeability, MDA concentrations, and Na+ concentrations in roots, stems, and leaves. The Na treatment significantly reduced K+, Ca2+, and Mg2+ concentrations in roots, but increased K+ concentrations in stems. Compared with the Na treatment, 39% of the leaves showed wilting symptoms in the Na+Ca treatment. The Na+Ca treatment significantly decreased leaf O-2(.-) production rates, H2O2 concentrations, cell membrane permeability, and MDA concentrations. Moreover, the Na+Ca treatment (1) significantly reduced Na+ concentrations in roots, stems, and leaves; (2) significantly increased root K+ concentrations; (3) significantly increased K+/Na+ ratios in roots; (4) significantly increased Ca2+ concentrations in stems and leaves, and Mg2+ concentrations in roots. In conclusion, exogenous CaCl2 reduces NaCl stress in sour jujube by reducing Na+ concentrations and increasing K+, Ca2+, and Mg2+ concentrations in various plant organs.