Increased CO2 concentrations increasing water use efficiency and improvement PSII function of mulberry seedling leaves under drought stress.

In this paper, the effects of different CO₂ concentrations (400 and 800 μmol·mol⁻¹) on photosynthetic gas exchange and chlorophyll fluorescence of mulberry (Morus alba L.) seedling leaves under drought stress were studied using an artificial climate chamber. The results showed that under non-drought conditions, the stomatal concentrations (G_s) and transpiratration rate (T_r) of mulberry seedling leaves decreased slightly with increased CO₂ concentrations, but the net photosynthetic rate (P_n) increased significantly. Under mild drought stress (5 days of drought), higher CO₂ concentrations significantly affected the photosynthetic gas exchange of mulberry seedling leaves, but had little effect on chlorophyll fluorescence. Under severe drought stress (10 das of drought), increased CO₂ concentrations not only alleviated drought stress by increasing the WUE of mulberry seedling leaves, but also significantly increased its PSII photochemical activity, which promoted electron transfer on the PSII acceptor side. In conclusion, increased CO₂ concentrations could raise the WUE of mulberry seedling leaves under normal water conditions and drought stress, and this effect was more significant under drought stress. Under severe drought stress, increased CO₂ concentrations improved the drought resistance of mulberry seedlings by improving their PSII function. [ABSTRACT FROM AUTHOR]