中文摘要：

以2a生胡杨实生苗为材料,采用盆栽称重法研究轻度（持续干旱6d）、中度（持续干旱12d）和重度（持续干旱18d）干旱及旱后复水过程中幼苗光合气体交换、叶绿素荧光参数及光合色素、可溶性糖、丙二醛（MDA）等含量的变化,探讨不同程度干旱及复水过程中胡杨幼苗生理生化响应与旱后恢复能力的关系。结果表明：（1）持续干旱,幼苗叶片光合速率（Pn）、有效光化学量子效率（Fv/Fm）、PSII反应中心光捕获效率（Fv＇/Fm＇）、实际光化学量子效率（ΦPSII）及光合色素含量均随干旱时间的延长和土壤含水量的减小逐渐下降;轻度和中度胁迫幼苗Pn分别下降了25%和60%,但Fv/Fm、Fv＇/Fm＇、ΦPSII与对照无显著差异（p〉0.05）,较短期的缺水条件下幼苗光合系统稳定;重度胁迫,幼苗Pn接近零,光合几乎完全受抑,Fv/Fm下降17%,长期缺水致使幼苗光合器官受损。（2）中度和重度干旱胁迫,幼苗叶片丙二醛含量显著,细胞膜遭到破坏;幼苗可溶性糖、Chl a/b、非光化学猝灭系数（NPQ）增大,其通过渗透调节提高抗旱性,减少光捕获及热耗散以避免过剩光对光合机构造成更大损伤;（3）轻度和中度胁迫后复水,幼苗光合、荧光参数均在短期内快速恢复,重度胁迫也在复水8d完全恢复,反映了幼苗较强的旱后修复能力;轻度胁迫幼苗叶片Pn和叶绿素含量均显著高于对照,表现出补偿效应,表明适度干旱诱导了幼苗的抗旱适应性。研究发现,干旱胁迫对胡杨幼苗光合生理具有显著抑制作用,但胡杨通过一些列光保护、光适应机制以及渗透调节等使其在干旱胁迫环境下生存,并能够在复水后完全恢复。

英文摘要：

Potted seedlings of 2a Populus euphratica were exposed to draught for 6d, 12d and 18d respectively and weighed to determine the changes in leaf gas exchange, chlorophyll fluorescence, and content of Chlorophyll, Malondialdehyde （MDA） and sugar through exposing to progressive drought and subsequent re-watering. The result showed that. i） seedlings were decreased in photosynthetic rate （Pn）, the effective quantum-use efficiency of PSII （Fv＇/Fm＇）, effective quantum yield of PSII photochemistry（ФPSII） and photosy＇nthetic pigment content, with the time extension exposed to draught and soil water content decrease; ii） moderate and severe draught caused increase of Malondialdehyde, damage to cell membrane, increase of soluble sugar, Chl a/b, non-photochemical quench （NPQ）, and decline of light capture or heat release to avoid more damage; iii） On re-watering under mild and moderate stress, fluorescence parameter and photosynthesis restored quickly, while 8d after re-watering under severe stress, indicating the stress resistance of seedlings. Pn and chlorophyll under mild stress were higher than control, indicating draught induced the adaptation. The research revealed that water stress restricted photosynthesis of P. euphratica seedling but some mechanism like photo adaptation and osmotic adjustment help to restore after re-watering.