中文摘要：

以塔里木盆地珍稀渐危种灰胡杨（Populus pruinosa Schrenk）为材料,研究其蒸腾速率（Tr）、气孔导度（Gs）、水汽压差（VPD）日变化及互动关系,以期揭示灰胡杨适应干旱荒漠环境的蒸腾耗水调控机理。结果表明,生长季灰胡杨Tr、Gs和VPD日变化均呈单峰曲线,总体随时间进程呈下降趋势;Tr、VPD峰值均滞后于Gs,这是上午时段Tr对VPD的响应阈值明显高于Gs对VPD的响应阈值所致。灰胡杨Tr与Gs、VPD及上午Gs与VPD均呈二次曲线关系,VPD对Tr、Gs均具双重作用,形成机制在于低VPD下Gs随VPD上升而增大,促进Tr升高;高VPD下Gs逐渐下降,引起Tr降低。数理统计分析表明,Gs是调控灰胡杨Tr的主导因素,而VPD通过Gs间接影响Tr。不同时段Tr的气孔调节机制不同,上午气孔调节为前馈式反应,下午为反馈式反应。综上所述,荒漠区灰胡杨Tr对Gs的响应敏感度高于对VPD,气孔调节是维持水分平衡的重要机制;VPD协同Gs来控制灰胡杨Tr,高VPD下引起叶片气孔关闭以降低蒸腾,维持树体水分平衡达到在干旱荒漠环境下生存的目的。

英文摘要：

In order to elucidate the mechanism of Populus pruinosa surviving to extreme arid region in northwest China, daily variations of transpiration rate（ Tr）, stomatal conductance（Gs） and vapor pressure deficit （VPD） and their relationships were analyzed. The diurnal variations of Tr, Gs and VPD of P. pruinosa were single - peak - curves in growing seasons, they all decreased gradually with time. The peaks of Tr and VPD were behind Gs, because of the response threshold of Tr to VPD was obviously higher than that of Gs to VPD. Quadratic curves were observed among Tr to Gs, VPD and Gs to VPD in moming. VPD had dual function to Tr and Gs, the formation mechanism was that Gs increased with VPD ascending to promote Tr in low VPD condition, but Gs declined gradually with VPD ascending to reduce Tr in high VPD condition. Multivariate statistical analysis found Gs was the dominant factor affecting Tr, while VPD via Gs was an indirect effect to affect Tr. Tr was adjusted via feed forward feedback in the morning, while in the afternoon via feedback mechanism. The results suggest that stomatal regula- tion of P. pruinosa was an important mechanism adjusting water balance, response sensitivity of Tr to Gs was higher than that of VPD, Tr was simultaneously controlled by VPD and Gs, higher VPD resulted in stomatal closure to reduce transpiration, which helped the water balance and improved its survival in the arid region.