Abstract
Drought is a critical limiting factor affecting the growth and development of plants in arid and semi-arid areas.Photosynthesis,one of the most important physiological processes of plants,can be significantly inhibited by drought.Photosystem Ⅱ(PSⅡ)is considered the main attack target when photosynthesis is affected by drought.To clarify how PSⅡ components of the ephemeral plant Erodium oxyrhinchum(grown in the Gurbantunggut Desert,China)respond to drought treatment,we evaluated the functional activity of PSⅡ by determining chlorophyll fluorescence and gas exchange parameters under different drought treatment levels(control(400 mL),moderate drought(200 mL),and severe drought(100 mL)).Under moderate drought treatment,significant decreases were found in net photosynthetic rate(Pn),effective quantum yield of PSⅡ(Y(Ⅱ)),relative electron transfer rate of PSⅡ(r ETR(Ⅱ)),oxygen-releasing complex,probability of an absorbed exciton moving an electron into the electron transport chain beyond primary quinone receptor QA-(Φ(Eo)),probability of a trapped exciton moving an electron into the electron transport chain beyond primary quinone receptor QA-(ψ(Eo)),and performance index of PSⅡ(PIabs).Compared to control treatment,marked increases were observed in water use efficiency(WUE),relative variable fluorescence at the J step(VJ),initial fluorescence(Fo),and dissipated energy per active reaction center(DIo/RC)under moderate drought treatment,but there were no substantial changes in semi-saturated light intensity(IK),active reaction centers per cross-section(RC/CS),and total performance index of PSⅡ and PSI(PItotal,where PSI is the photosystem Ⅰ).The changes of the above parameters under severe drought treatment were more significant than those under moderate drought treatment.In addition,severe drought treatment significantly increased the absorbed energy per active reaction center(ABS/RC)and trapping energy per active reaction center(TRo/RC)but decreased the energy transmission connectivity of PSII components,RC/CS,and PItotal,compared to moderate drought and control treatments.Principle component analysis(PCA)revealed similar information according to the grouping of parameters.Moderate drought treatment was obviously characterized by RC/CS parameter,and the values of Fo,VJ,ABS/RC,DIo/RC,and TRo/RC showed specific reactions to severe drought treatment.These results demonstrated that moderate drought treatment reduced the photochemical activity of PSⅡ to a certain extent but E.oxyrhinchum still showed strong adaptation against drought treatment,while severe drought treatment seriously damaged the structure of PSⅡ.The results of this study are useful for further understanding the adaptations of ephemeral plants to different water conditions and can provide a reference for the selection of relevant parameters for photosynthesis measurements of large samples in the field.
基金项目
National Natural Science Foundation of China(U2003214)
Western Youth Scholars Project of the Chinese Academy of Sciences(2021-XBQNXZ-006)
国家科技期刊平台
NSTL
万方数据