Effects of exogenous Ca2+ 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 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.

Effects of NaCl stress on stomatal traits, leaf gas exchange parameters, and biomass of two tomato cultivars.

To understand the mechanism underlying responses of stomatal traits, gas exchange parameters, and biomass of tomato plants to salt stress, two tomato cultivars (Shed and Alam) were treated by salt stress by adding NaCl (0.1 mol·L-1) to nutrition medium in environmental growth chambers for 90 days. Our results showed that salt stress substantially decreased the stomatal density, stomatal width, stomatal area, and stomatal area index of Shed by 32%, 45%, 25%, and 49%, respectively. The stomatal traits of Alam were not affected by NaCl treatment. The spatial scales of the regular stomatal distribution pattern of Shed and Alam were significantly decreased by 30% and 43%, and the nearest neighbor distance Lhat (d) of shed cultivar was increased by 20% under salt stress. NaCl stress resulted in marginal declines in the net photosynthetic rates (Pn), stomatal conductance (gs), transpiration rates (Tr) of both cultivars. The decrease of the photosynthetic rate of Shed under salt stress resulted from stomatal limitation, whereas the Pn of Alam was subjected to non-stomatal constraints. NaCl stress substantially decreased the seedling biomass of both cultivars, and the decline of belowground biomass was higher than that of aboveground biomass. Overall, our results suggested that the Alam cultivar is more salt-tolerant than Shed.

[Changes of non-structural carbohydrates and its impact factors in trees: a review].

Non-structural carbohydrates (NSCs) are an important energy source for the metabolism of plants. The size of the NSC pool is likely to mirror the overall carbon supply status and its dynamics strongly influences physiological processes in plants. In order to predict the response and adaptation of trees to climate change, this review summarized the current understanding of NSC pool in trees, and mainly focused on its seasonal and spatial variation for analyzing the relationships between environmental factors and NSC allocation. Moreover, the response and adaptation strategies of NSC pool in trees to climate change were also discussed. Finally, some suggestions were proposed for the potential study orientation of NSC pool in trees in future climate conditions.