短期干旱和复水对麻栎幼苗光合及叶绿素荧光的影响

麻栎是鲁中山区森林植被恢复的重要阔叶树种之一，本文以1年生麻标幼苗为试验对象，研究短期干旱和复水对其光合及叶绿素荧光等生理生态特征的影响。结果表明：在干旱胁迫初期，干旱组的各项指标均优于对照组，说明过高的土壤含水量并不利于麻栎幼苗的生长；随着土壤干旱程度的进一步加剧，幼苗的气孔导度减少，导致光合和蒸腾作用的下降，水分利用效率升高；胁迫末期各项光合指标均降到最低。从叶绿素荧光参数可以看出，干旱胁迫并未使幼苗的光合机构发生伤害，幼苗在适宜的水分条件时产生光合能力上调，当水分匮缺时，以叶黄素循环为主的非光化学淬灭耗散掉过剩的光能达到保护光合机构的目的。复水后麻栎幼苗的各项生理生态指标恢复正常，但气孔导度的增大存在一定的滞后效应，导致了水分利用效率的反冲，同时叶黄素库仍然维持较高水平，麻栎幼苗通过物理和化学的双重保护来抵御干旱胁迫和进行胁迫后的恢复。

Effects of short-term drought and rewatering on photosynthesis and chlorophyll fluorescence of Quercus acutissima seedlings

Quercus acutissima is one of the most important deciduous broadleaf species for the reforestation in the center of Shandong mountain areas. We chose the one- year- old Q. acutissima seedlings to study the effects of short- term drought and rewatering on the photosynthesis and chlorophyll fluorescence. From the results, we detected that these parameters were better in the drought treatments than the controls. It was disadvantage for Q. acutissima seedlings to grow in the moist soil. With the drying of soil, the stomatal conductance became decreased, which led to the reduction rate of the photosynthesis and transpiration. Accordingly, the water use efficiency was enhanced. At the end of the drought treatment, every photosynthetic parameter reached its lowest value. The short-term drought stress did not damage the photosystem from the values of chlorophyll fluorescence. The photosynthetic up-regulation occurred at the early period of drought. The thermal dissipation depending on the xanthophyll cycle protected the photosystem from photoinhibition at the lack of water supply. The recovery of each parameter happened after the rewatering. There was the hysteresis on the increase of stomatal conductance, which led to the overshoot of water use efficiency. The pool of xanthophyll cycle remained at a high level. The double protections of mechanical and chemical mechanisms insured the seedlings to tolerate and recover to the stress.