Effects of exogenous Ca on stomatal traits, photosynthesis, and biomass of maize seedings under salt stress.

Understanding the responses of stomatal structure, photosynthesis and biomass of maize to exogenous Ca addition under NaCl stress has important significance for further uncovering the alleviative mechanism of exogenous Ca on maize under salt stress. We examined the effects of exogenous Ca(0, 5, 10, 20, 40, 80 mmol·L) on the stomatal structure, photosynthesis and biomass of maize (Zea mays L. cv. Jingke 665) seedlings under NaCl stress (100 mmol·L). Our results showed that exogenous Ca 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 (P) initially increased and then decreased with the increases of exogenous Ca concentration, whereas both the stomatal conductance (g) and intercellular CO concentration (C) were decreased, suggesting that the decrease of P was mainly due to stomatal limitation under high Ca concentration. The biomass of maize seedlings was increased and the root/shoot ratio was decreased with the increases of exogenous Ca concentration, suggested that the alleviated effect of exogenous Ca on aboveground biomass was higher than that on belowground biomass of maize under salt stress.