RESUMO
Understanding the responses of stomatal structure, photosynthesis and biomass of maize to exogenous Ca2+ addition under NaCl stress has important significance for further uncovering the alleviative mechanism of exogenous Ca2+ on maize under salt stress. We examined the effects of exogenous Ca2+(0, 5, 10, 20, 40, 80 mmol·L-1) on the stomatal structure, photosynthesis and biomass of maize (Zea mays L. cv. Jingke 665) seedlings under NaCl stress (100 mmol·L-1). Our results showed that exogenous Ca2+ addition had limited effect on stomatal density, but significantly decreased stomatal shape index, stomatal area, stomatal length, stomatal width, and stomatal cir-cumference. Meanwhile, the net photosynthetic rate (Pn) initially increased and then decreased with the increases of exogenous Ca2+ concentration, whereas both the stomatal conductance (gs) and intercellular CO2 concentration (Ci) were decreased, suggesting that the decrease of Pn was mainly due to stomatal limitation under high Ca2+ concentration. The biomass of maize seedlings was increased and the root/shoot ratio was decreased with the increases of exogenous Ca2+ concentration, suggested that the alleviated effect of exogenous Ca2+ on aboveground biomass was higher than that on belowground biomass of maize under salt stress.