Exogenous calcium-alleviating effect on sodium salt-induced phytotoxicity associated with changes in photosynthetic characteristics of wheat seedlings

To evaluate the Ca-alleviating effect on sodium salt-induced phytotoxicity, wheat (Triticum aestivum L.) cultivar Xihan 3 seedlings were treated with 150 mM NaCl, CaCl2 (0.1, 0.5, and 1 mM), Ca2+-channel blocker LaCl3, and/or Ca2+ chelator, ethylene glycol tetraacetic acid (EGTA) alone or in combination, to investigate seedling growth and photosynthetic characteristics. NaCl (150 mM) exposure alone suppressed a growth of seedling, weakened photosynthetic efficiency and chlorophyll (Chl) fluorescence parameters, reduced photosynthetic pigments, Ca2+ and calmodulin (CaM) contents, and downregulated TaCaM expression in wheat leaves. The opposite changes of these parameters were caused by 0.5 or 1 mM CaCl2 treatments alone. Moreover, 0.5 or 1 mM CaCl2 application effectively alleviated sodium salt-induced changes of these parameters, which was blocked by LaCl3 or EGTA. Therefore, exogenous Ca presence effectively promoted the growth of NaCl-stressed wheat seedlings through the enhancement of photosynthesis and Chl synthesis mediated by the Ca-CaM signal.