紫花苜蓿光合特性对不同程度干旱的响应差异性分析OA

Drought has seriously affected the growth of alfalfa(Medicago sativa)and restricted the development of the alfalfa industry in Xinjiang.In this study,an analysis of alfalfa photosynthetic characteristics that differ in response to different degrees of drought stress was carried out using'Xinmu No.4'and'WL525HQ'lines of alfalfa as the experimental materials.Our results showed that drought significantly reduced the relative water content of alfalfa leaves,the pigment content per unit area of alfalfa,net photosynthetic rate,intercellular CO2 concentration,and stomatal conductance and significantly affected the stomatal morphology.However,different degrees of drought stress had different effects on the photosynthesis of alfalfa leaves.Under mild drought,the stomatal opening of alfalfa decreased significantly while the photosystem Ⅱ(PSⅡ)and photosystem Ⅰ(PSⅠ)activities and ribulose-1,5-bisphosphate carboxylase/oxygenase(Rubisco)and rubisco activase(RCA)enzyme activity did not significantly differ.Under moderate drought,Rubisco,RCA,and carotenoid significantly decreased,NADP-Malate Dehydrogenase(NADP-MDH)and glycolic acid oxidase(GO)significantly increased,and PSⅡ and PSⅠ activities did not significantly change.Under severe drought,the PSⅠ and PSⅡ activities,carotenoids,Rubisco,RCA,and NADP-MDH decreased significantly while the GO levels increased.This indicated that under mild drought,stomatal closure caused photosynthetic decline.Under moderate drought,the malate shuttle pathway and photorespiration were significantly up-regulated in alfalfa leaves to alleviate the over-reduction of the photosynthetic electron transport chain,and decreases in photosynthetic carbon assimilatory enzyme activity and stomatal closure were the main reasons for the decline in photosynthesis.Under severe drought,the photoprotective pathway was significantly decreased and the combination of photosystem activity,decreased photosynthetic carbon assimilatory enzyme activities,and stomata closure led to the decline in photosynthesis.