Department of Silviculture, Institute of Forestry and Rural Engineering, Estonian University of Life Sciences, Kreutzwaldi 5, Tartu 51014, Estonia.
Tree Physiol. 2011 Aug;31(8):855-64. doi: 10.1093/treephys/tpr078. Epub 2011 Aug 19.
To clarify interactions between stomatal responses to two simultaneous environmental changes, the rates of change in stomatal conductance were measured after simultaneously changing two environmental factors from the set of air humidity, leaf water potential (hydraulic environmental factors), air CO(2) concentration and light intensity (photosynthetic environmental factors). The stomatal responses to changes in leaf water potential were not significantly modified by any other simultaneous environmental change. A decrease in air humidity was followed by a decrease in stomatal conductance, and an increase in air humidity was followed by an increase in the conductance, irrespective of the character of the simultaneous change in the photosynthetic environmental factor. If the simultaneous change had an opposite effect on stomatal conductance, the rate of change in stomatal conductance was higher than the theoretical summed rate-the sum of the rate following one environmental change and the rate following another environmental change, measured separately. That is, the stomatal response to air humidity dominated over the responses to photosynthetic environmental factors. Yet, if the simultaneous change in photosynthetic factors had a codirectional effect on stomatal conductance, the rate of stomatal conductance change was lower than the theoretical summed rate. After a simultaneous change of two photosynthetic environmental factors, the rate of stomatal conductance change was very similar to the theoretical rate, if both the environmental changes had a codirectional effect on stomatal conductance. If the changes in the photosynthetic factors had opposite effects on stomatal conductance, the conductance increased, irrespective of the character of the increasing environmental factor. In drought-stressed trees, the rates of change in stomatal conductance tended to differ from the theoretical summed rates more than in well-watered trees. Stomatal closure following an increase in CO(2) concentration was the stomatal response that was most strongly suppressed by the response to another simultaneous environmental change. Six species of temperate deciduous trees were shown to be similar in their relations between the stomatal responses to two simultaneous environmental changes. The mechanism and ecological significance of the interactions between the two signal response pathways of stomata are discussed.
为了阐明气孔对两种同时发生的环境变化的相互作用，我们同时改变了空气湿度、叶片水势（水力环境因素）、空气 CO2 浓度和光强（光合环境因素）这组环境因素中的两个，测量了气孔导度的变化率。气孔对叶片水势变化的响应不受任何其他同时发生的环境变化的显著影响。空气湿度降低导致气孔导度降低，空气湿度升高导致导度升高，而不论光合环境因素同时发生的变化的性质如何。如果同时发生的变化对气孔导度有相反的影响，那么气孔导度的变化率就会高于理论总和——一个环境变化的变化率和另一个环境变化的变化率之和，这两个变化率是分别测量的。也就是说，气孔对空气湿度的响应超过了对光合环境因素的响应。然而，如果光合因素的同时变化对气孔导度有同向作用，那么气孔导度变化的速率就会低于理论总和。在两个光合环境因素同时发生变化后，如果两个环境变化对气孔导度都有同向作用，那么气孔导度变化的速率非常接近理论速率。如果光合因素的变化对气孔导度有相反的影响，那么无论增加的环境因素的性质如何，导度都会增加。在干旱胁迫下的树木中，气孔导度变化的速率比在水分充足的树木中更倾向于偏离理论总和。CO2 浓度升高后气孔关闭，这是气孔对另一种同时发生的环境变化的响应最强烈的抑制。六个温带落叶树种在对两种同时发生的环境变化的气孔响应之间的关系上表现出相似性。讨论了两种气孔信号响应途径之间相互作用的机制和生态意义。
