中文摘要：

采用人为控制土壤含水量的方法对欧李进行轻度和重度干旱的处理,测定叶片的气体交换和叶绿素荧光参数的日变化。结果表明,干旱胁迫下欧李叶片净光合速率、蒸腾速率、水分利用效率、气孔导度、PSII最大光化学效率、光化学量子效率显著下降,但胞间CO2浓度、非光化学猝灭系数以及叶黄素循脱环氧化状态（Z＋0.5A）/（V＋A＋Z）和Z含量升高。两干旱处理植株的影响程度存在差异。这表明在长时间干旱条件下,欧李叶片光合作用的降低受到气孔与非气孔因素的双重影响,叶黄素循环的启动增加了胁迫条件下的热耗散能力以保护光合机构免受干旱胁迫的进一步伤害。

英文摘要：

In order to study the light response mechanisms of Cerasus humilis under drought stress,leaf gas exchange and chlorophyll fluorescence parameters were measured with mild and severe drought treatment.The results showed that net photosynthesis rate（Pn）,transpiration rate（E）,water utilization efficiency（WUE）,stomatal conductance（Gs） and maximal photochemical efficiency of PSⅡ（Fv/Fm） decreased significantly in seedlings of C.humilis under drought stress.While the values of intercellular CO2 concentration（Ci）,non-photochemical quenching coefficient（NPQ） and the ratio of Z＋0.5A and V＋A＋Z increased.These results indicated that the decrease of photosynthetic capacity was attributed to both stomatal limitation and non-stomatal limitation under long drought treatment.The capacity of heat dissipation was improved by initiating of the xanthophyll cycle,which resulted in the protection of the photosynthetic apparatus from the damage of drought stress.