土壤持续干旱对白杨幼苗光合生理的影响

以3—4月龄的白杨幼苗作为材料，采取土壤逐渐干旱的方法进行控水试验，对白杨幼苗的叶片相对含水量 （RWC）、茎干木质部水势 （ψxp）、荧光参数、气体交换、叶面积等指标进行抗旱性综合评价。结果表明：干旱初期，白杨幼苗叶片RWC和ψxp均已显著下降，至阶段2 （几乎所有叶片都萎蔫），RWC和ψxp均几乎降至最低值，继续干旱，这些值变化不明显。所有叶片枯死后继续停止浇水1个月后进行复水，从老叶脱落的位置又长出新叶，新叶的RWC和ψxp基本恢复至对照水平，但Pn和gs增幅不显著。植株受到严重干旱胁迫伤害之后，叶片净光合速率 （Pn） 及气孔导度 （gs） 降幅显著，且复水后叶片光合系统的修复比较缓慢，有的甚至是不可逆的伤害。白杨幼苗最大光化学量子产量比较稳定，受干旱胁迫的影响较小。

Effects of Soil Drought on Photosynthetic Physiology of Populus tremuloides Seedlings

In this experiment, 3-4 month old Populus tremuloides seedlings were used as materials for controlled water test by soil progressive drought method, and then the leaf relative water content (RWC), stem xylem water potential (ψxp), fluorescence parameters, gas exchange and leaf area index were measured to comprehensive evaluation of drought resistance of poplar seedlings. The results showed that leaf RWC, ψxp, stomatal conductance (gs) and net photosynthetic rate (Pn) were decreased significantly at the early stage of drought. To stage 2, these parameters almost dropped to their valleys, and they had no obvious variation even implemented continue drought. After all leaves were dead and remained one month no watering, and then re watered, new leaves grow from the old leaf position. Leaf RWC and ψxp of new leaves returned to the control level, but Pn and gs had no obvious increase. Under severe drought stress damage, Pn and gs reduced significantly, and photosynthetic system repair was relatively slow, and even some was irreversible damage. The photochemical quantum yield (Fv/Fm) was more stable, and less affected by drought stress.