渐进式干旱对辽东栎幼树光合特性的影响及敏感性分析

Effects and Sensitivity of Progressive Drought on Photosynthetic Characteristics of Quercus liaotungensis Seedlings

[目的]探究辽东栎幼树叶片的光合系统对土壤渐进式干旱的响应,并筛选干旱敏感性指标。[方法]采用盆栽渐进式干旱胁迫法,对2年生辽东栎幼苗叶片的叶倾角、叶绿素荧光、光合作用等指标进行方差分析(ANOVA)和LOESS非线性拟合。[结果]渐进式干旱对光合气体交换的影响最显著,其次是叶倾角,最后是光系统Ⅱ(PSⅡ)的电子传递和能量耗散。依据土壤相对含水量(SRWC)对光合特性的影响,辽东栎幼树光合系统的干旱响应可划分为4个阶段:第1阶段(胁迫未发生,26%>SRWC>20%),光合气体交换参数无下降;第2阶段(中度胁迫,20%>SRWC>14%),气孔限制效应明显,叶倾角降低至-14.0±1.7°;第3阶段(重度胁迫,14%>SRWC>8%),叶片水分利用效率(WUE)显著下降,叶倾角值降低至-43.2±10.3°,光合气体交换明显减少,表明SRWC降低至14%是辽东栎幼树的灌溉临界值;第4阶段(极度胁迫,SRWC<8%),PSⅡ的电子传递和能量耗散显著改变,光合机构严重受损,叶倾角值降低至-68.5±6.7°,表明SRWC降低至8%是辽东栎幼树叶片的致死临界值。基于叶倾角对土壤干旱的响应存在阶段性差异,其可作为辽东栎幼树灌溉临界值的预警指标;PSⅡ单位面积有活性反应中心数量RCO/CS、单位反应中心吸收的能量ABS/RC、单位反应中心以热能形式耗散的能量DIO/RC、叶片性能指数PIABS可作为叶片致死的预警指标。[结论]本研究观察到辽东栎幼树叶片光合系统对土壤干旱的响应存在阶段性差异,据此确定了灌溉临界值和反映土壤干旱的敏感性指标,可以为辽东栎幼树高效灌溉策略的制定提供理论基础。

[Objective]To investigate the response of photosynthetic system of leaves in Quercus liaotungensis seedlings under progressive drought and select drought sensitive indicators.[Method]Based on the progressive drought stress method in pots,we performed variance analysis(ANOVA)and LOESS nonlinear fit on leaf droop angle,chlorophyll fluorescence,and photosynthesis of 2-year-old Q.liaotungensis seedlings.[Result]The results indicated that progressive drought had the most significant effect on photosynthetic gas exchange,followed by leaf droop angle and electron transfer and energy dissipation of PSII.According to the influence of soil relative water content(SRWC)to photosynthetic characteristics,the drought response of the photosynthetic system of Q.liaotungensis seedling could be classified into four stages:Stage I(no stress,26%>SRWC>20%),photosynthetic gas exchange parameters did not drop;Stage II(moderate stress,20%>SRWC>14%),the effect of stomatal restriction was evident and the leaf droop angle was lowered to-14.0±1.7°;Stage III(high stress,14%>SRWC>8%),the water use efficiency(WUE)of leaf and the gas exchange parameters decreased significantly,and the leaf droop angle was lowered to-43.2±10.3°,which indicated that SRWC lowered to 14%was the irrigation water threshold values for Q.liaotungensis seedling;Stage IV(extreme stress,SRWC<8%),the electron transport and energy dissipation of PSII changed significantly,the photosynthetic apparatus were severely damaged,the leaf droop angle was lowered to-68.5±6.7°indicated that SRWC lowered to 8%was the lethal threshold for leaf of Q.liaotungensis seedling.Based on the stage differences in the leaf droop angle responses to soil drought,it could be used as the warning index of the irrigation water threshold value of Q.liaotungensis seedlings.The number of reaction centers per unit area in PSII(RCO/CS),the absorption flux per reaction center in PSII(ABS/RC),the flux of energy dissipated in processes other than trapping per active in PSII(DIO/RC),and the leaf performance index(PIABS)could be used as warning indexes of the lethal threshold for leaf.[Conclusion]In this study,the stage differences of the photosynthetic system of Q.liaotungensis seedling‘s leaf response to soil drought were observed,therefore determining the irrigation water threshold values and sensitivity indicators reflecting soil drought,which provides a theoretical basis for developing an efficient irrigation strategy for Q.liaotungensis seedlings.