EGI OpenIR  > 研究系统  > 荒漠环境研究室
Thesis Advisor李君
Degree Grantor中国科学院大学
Place of Conferral新疆乌鲁木齐
Degree Discipline理学硕士
Keyword干旱 复水 胡杨 气孔限制 叶肉限制 生化限制 drought recovery Populus euphratica stomatal limitation mesophyll conductance limitation biochemical limitation
AbstractStomata play a key role in regulation the trade-off between photosynthesis andtranspiration. Drought stress may reduce evaporation rate at the cost of carbon assimilationloss through stomatal closure, which suggests that stomatal regulation is critical to balancewater and carbon under different soil moisture conditions. As the constructive species ofTarim desert riparian forests in northwestern china, Populus euphratica is subject tofrequent groundwater fluctuations due to the variations in runoff, which gets P.euphratica,especially for seedlings established on the sediments close to active channel, frequentlysuffer from drought in dry seasons and re-watering after flooding events. Currently little isknow about the role of stomatal behavior of P.euphratica in adapting to such frequentfluctuations in water environments. The dominant species of P.euphratica was chosen inthis study. In this study, we measured photosynthesis responses to CO2, cholorophyllfluorescence, water status and hydraulic architecture parameters for 3 years oldP.euphratica seedling during a progressive drought as well as re-watering. Then thestomatal and non-stomatal limitations for photosynthesis of P.euphratica were analysedduring the progressive drought and after re-watering.The results indicated that, when the xylem water potential decreased to -0.41 MPa forseedling experiencing 11 d drought, the transpiration rate (Tr), electron transport rate(ETR), respiration rate (Rd), stomatal conductance (gs), mesophyll conductance (gm),photospiration rate (Pr), substomatal CO2 concentration (Ci), chloroplast CO2 concentration(Cc) and maximum capacity for carboxylation (Vcmax) decreased while water use efficiency (WUE) increased and the carbon assimilation rate was maintaineds at a high level. At thisearly drought stage, biochemical limitation (BL) was the major limitation to photosynthesis.With the xylem water potential decreasing from -1.28 MPa after 47 d drought, the WUE,Pr and Rd increased, the gs, gm, ETR, Vcmax, Ci, Cc and Tr exhibited varying decease, whichsuggests that shown carbon assimilation mainly limited by SL at this stage. The xylemwater potential further decreasing to -1.52 MPa after 79 drought, the WUE, gs, Tr, ETR, gm,Vcmax, Pr and Rd continued to decrease while Ci and Cc increase, showing a important roleof MCL in maintaining low carbon assimilation rate at this stage. Overall, results theprogressive drought experiment show that, under light drought stress, P.euphraticaseedling are able to maintain high carbon assimilation rate through WUE injustment, withBL as the major limitation on photosynthesis. Under medium drought stress, the reduced gsand carbon assimilation rate along with increased WUE suggest that carbon assimilation islimited by SL. Under severe drought stress, An was mainly limited by MCL, evidenced bydecreased WUE and carbon assimilation rate.For seedlings rewatered at a xylem water potential of -0.98 MPa, Vcmax recoveredcompletely while An unlimited by BL at the time, recovered to 52.98% relative to thecontrol on the 1st day after re-watering. The gs and gm recovered almost completely on the4th day after re-watering, at the time An was 99.35% relative to the control and not limitedeither by SL or by MCL. During the re-watering period, PLC was negatively related to gsand An. For seedlings rewatered at the xylem water potential of -1.52 MPa, Vcmax totallyrecovered while An was restored to 48.78% of the control on 2nd day after re-watering,without limitation by BL. The gm recovered to 93.70% of the control on the 4th day afterre-watering, showing no MCL limitation on An. The gs recovered only to 56.17% of thecontrol on the 5th day after rewatering, showing a major limitation of SL on An. Severelydroughted seedlings under rewatering showed a negative relationship between gs, An andPLC but a positive one between gs, An and KL, KS. In conclusion, results of re-wateringexperiment show that An of the moderately-droughted seedling is little limited by SL, MCLand BL after re-watering, leading to a rapid recovery of An. SL was the major limitation on An for severly droughted seedlings when rewatered. The recovery of PLC, KS and KL maycontribute to the recovery of An in P.euphratica. Furthermore, comparing recovery of Anand limlit factors to photosynthesis under different degrees of drought stress afterre-watering, which find that the realtively rapid recovery of carbon assimilation forP.euphratica seedling that the main reason were quickly recovery of MCL and BL underrewatering.
Other Abstract气孔是叶片水、碳交换的重要通道。干旱胁迫时,植物可通过关闭气孔减少水分蒸腾,但以减少碳同化为代价,表明气孔调节是植物在不同水分条件下控制水碳平衡的关键。胡杨是我国西北干旱区塔里木河流域的建群种,受干旱区的河流径流变化的影响,其生境面临着周期性干旱和复水的变化,尤其是靠近河道附近的幼龄胡杨。胡杨如何通过气孔行为调节适应这种水分生境的变化,我们对此知之甚少。本文以幼龄胡杨为研究对象,通过测坑控制试验模拟逐步干旱和复水过程,同时设置对照组充分供水条件,测量了干旱及复水过程中胡杨叶片的CO2响应曲线、叶绿素荧光、枝条的木质部导水损失率、比导率、叶比导率、胡伯尔值及枝条水势等指标,分析逐步干旱过程中胡杨叶片光合的气孔限制和非气孔限制作用,以及干旱复水后胡杨叶片气孔导度的变化及其叶片光合限制作用。逐步干旱试验结果表明,干旱 11 d 后,胡杨凌晨水势降至-0.41 MPa,此时净光合速率(An)主要限制因素是生化限制(BL),其中气孔导度(gs)、叶肉导度(gm)、最大羧化效率(Vcmax)、胞间二氧化碳浓度(Ci)、暗呼吸速率(Rd)、光呼吸速率(Pr)、蒸腾速率(Tr)、电子传递速率(ETR)及叶绿体二氧化碳浓度(Cc)减少,水分利用效率(WUE)增大,叶片依然保持较高碳同化水平;干旱 47 d 后,凌晨水势降至-1.28 MPa,此时 An 主要限制是气孔限制(SL),WUE、Pr 及 Rd 增大, gs、Ci、Cc、gm、ETR、Vcmax 及 Tr 大幅度减少,叶片碳同化水平迅速降低;干旱 79 d后,凌晨水势降至-1.52 MPa,An 主要受叶肉导度限制(MCL),WUE、gs、Tr、gm、Vcmax、ETR、Pr 及 Rd减少,Ci 和 Cc 增大,叶片碳同化水平继续降低。逐步干旱试验表明,胡杨干旱早期叶片主要受 BL约束,至中度干旱胁迫后叶片光合主要受 SL约束,受重度干旱胁迫后叶片光合主要受 MCL约束。对不同干旱胁迫程度的胡杨进行了复水试验。结果表明胡杨凌晨水势降至-0.98MPa 后进行复水处理,复水 1 d 后 Vcmax可完全恢复,An 恢复至充分灌水的 52.98%,此时不受 BL影响;复水 4 d 后 gs 和 gm 基本恢复,An 恢复至充分灌水的 99.35%,此时基本不受 SL、MCL及 BL影响;在复水过程中木质部导水损失率(PLC)与 An和gs呈显著负相关关系。凌晨水势降至-1.52 MPa后进行复水处理,复水2 d后Vcmax可完全恢复,An恢复了48.78%,此时不受BL约束;复水4 d后gm恢复了92.73%,An恢复了93.70%,此时基本不受MCL和BL约束,复水5 d后gs仅仅恢复了56.17%,此时An恢复了95.11%,仍受SL影响;复水过程中胡杨gs、An与PLC呈显著负相关关系,其与叶比导率(KL)、比导率(KS)呈显著正相关。复水试验表明:轻度干旱复水后,胡杨An完全恢复,不受SL、MCL及BL的约束,且PLC恢复有助于An和gs的恢复。重度干旱复水后,SL是主要限制因子,但胡杨An仍可恢复至95.11%,这与MCL、BL快速恢复有关,且复水过程中PLC、Ks及KL的恢复均有助于的An和gs恢复。对比不同程度干旱复水后胡杨叶片光合能力及限制因子变化,发现胡杨叶片光合能力均可快速恢复,且MCL和BL的变化是胡杨在水分条件改善时决定其固碳功能恢复的关键因子。
Subject Area生态学
Document Type学位论文
First Author Affilication中国科学院新疆生态与地理研究所
Recommended Citation
GB/T 7714
周多多. 干旱及复水过程中胡杨气孔行为研究[D]. 新疆乌鲁木齐. 中国科学院大学,2017.
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