Effects of drought stress on photosynthetic characteristics in Hemsleya zhejiangensis / 中草药

ABSTRACT

Objective To investigate the requirement of water in Hemsleya zhejiangensis during the culture process. Methods The chlorophyll content, the gas exchange, and chlorophyll fluorescence parameter in H. zhejiangensis were measured after treatment with drought stress for different time. Results With decreasing of relative soil water content, the net photosynthetic rate (Pn) in H. zhejiangensis was increased before the 15 d and than was decreased. The stomatal conductance (Gs) and transpiration rate (E) were decreased under drought stress for 5 d, while the intercellular CO2 concentration (Ci) was increased. The efficiency of energy conversion of open PSⅡ (Fv′/Fm′) maintained rather stable, while its electron transport rate (ETR), actual PSⅡ efficiency (?PSⅡ), photochemical quenching (qP), and non-photochemical quenching (NPQ) were increased after the 10 d of drought stress, and then was decreased, which was consistent with the change in Pn. Conclusion The growth of H. zhejiangensis is promoted under slight drought stress condition, which is probably associated with the dissipation of excess light energy.