毛乌素沙地4种典型植物叶片凝结水吸收能力及其水分生理响应

  目的  明确毛乌素沙地4种典型植物沙蓬、软毛虫实、刺藜和苦豆子的叶片凝结水吸收能力，阐明植物叶片对凝结水浸润的水分生理响应。  方法  将受试植物置于用高丰度氘水配置的人工标记凝结水环境中，进行凝结水浸润处理，通过比较处理组和对照组植物叶水、根水及根际土壤水的稳定氢同位素丰度变化，确定受试植物叶片是否具有吸水能力，示踪叶片吸收凝结水后，是否将水分转移到植物根系及根际土壤之中；使用露点水势仪、电子天平及气孔计，测定受试植物处理前后的叶水势、叶片含水量和气孔导度变化，了解受试植物对凝结水浸润的水分生理响应。  结果  （1）高丰度氘标记凝结水浸润后，处理组4种受试植物的叶水δ2H（20‰ ~ 100‰）均显著高于对照组（?25‰ ~ ?15‰），而根水（?45‰ ~ ?30‰）及根际土壤水（?50‰ ~ ?40‰）则与对照组无显著差异；（2）经过凝结水浸润试验处理，沙蓬的叶水势升高23.81%，叶含水量升高2.94%，气孔导度降低57.40%；软毛虫实的叶含水量升高了2.45%，叶水势和气孔导度无显著变化；刺藜的叶水势升高了21.95%，气孔导度和叶含水量无显著变化；苦豆子的叶水势、叶含水量和气孔导度均无显著变化。  结论  毛乌素沙地4种典型植物叶片均具有凝结水吸收能力，叶片吸收的水分未被发现转移至根部或根际土壤。沙蓬、软毛虫实、刺藜通过叶片吸水显著改善了自身水分生理状态，这可能是其适应沙地严酷水分条件的重要水分利用机制，有助于植物存活，而苦豆子叶片对凝结水浸润无明显响应，不能有效利用叶片吸水改变其水分生理状态。 

Foliar condensate absorption capacity of four typical plant species and their physiological responses to water in the Mu Us Sandy Land of northwestern China

  Objective  In this study, we examined Agriophyllum squarrosum, Corispermum puberulum, Chenopodium aristatum, and Sophora alopecuroides in the Mu Us Desert of northwestern China to explore the ability of leaf condensate absorption and their physiological responses to water.  Method  We determined whether the condensate can be absorbed by the leaves of four plant species, and whether the absorbed water can be transported to the root and rhizosphere soil by dew covered experiments and stable isotope tracer technology to contrast the δ2H values of samples in the leaves, roots and rhizosphere soil from the treatment and control. Meanwhile, we measured leaf water potential (Ψ_L), leaf water content (w_L), and stomatal conductance (Gs) before and after dew treatment by dew point water potential meter, electronic balance and plant porometer in order to evaluate the effects of foliar condensate absorption on the species.  Result  (1) After the deuterium labelled condensate treatment, the δ2H values in samples of leaves (20‰?100‰) in the treatment group of four plant species were significantly higher than control (?25‰? ?15‰); the δ2H values in samples of root(?45‰ ? ?30‰) and rhizosphere soil (?50‰ ? ?40‰) in the treatment group did not change significantly compared with control. (2) After the dew treatment, Ψ_L, w_L of A. squarrosum increased by 23.81%, 2.49%, and Gs of it decreased by 57.40%, respectively; w_L of C. puberulum increased by 2.45%, but the Ψ_L and Gs were not change significantly; Ψ_L of C. aristatum increased by 21.95%, but the w_Land Gs were not change obviously; for S. alopecuroides, there were no significant differences in Ψ_L, w_L and Gs.  Conclusion  We find that all of the four plant species can absorb condensate through leaves, but the water cannot be transported to the root and rhizosphere soil. Agriophyllum squarrosum, Corispermum puberulum and Chenopodium aristatum could improve their water physiological state through water absorption. It may be an important water use strategy for them to adapt to drought environment, for this helps the plants to survive. However, Sophora alopecuroides does not significantly respond to foliar condensate absorption and also could not improve its water physiological state through this process.