The peaked response of transpiration rate to vapour pressure deficit in field conditions can be explained by the temperature optimum of photosynthesis
The peaked response of transpiration rate to vapour pressure deficit in field conditions can be explained by the temperature optimum of photosynthesis
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DOI：
10.1016/j.agrformet.2013.12.007
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发表时间：
2014-06-01
影响因子：
6.2
通讯作者：
McMurtrie, Ross E.
中科院分区：
文献类型：
--
作者：
Duursma, Remko A.;Barton, Craig V. M.;McMurtrie, Ross E.
叶片蒸腾速率（E）对水汽压亏缺（D）的增加常常表现出峰值响应。在高D，被称为“明显的前馈响应”，减少E的机制，是强烈的争论，但迄今为止的解释只集中在液压过程。然而，气孔也响应与光合作用相关的信号。我们调查了在田间E对D的明显前馈响应是否可以用光合作用对温度（T）的响应来解释，温度（T）通常与田间条件下的D共同变化。由于光合作用随着T的增加而降低，超过其最佳值，它可能会导致气孔导度（g（s））的降低，这是g对单独增加D的响应的补充。如果这种额外的下降足够陡峭，并且A和gs之间发生耦合，则可能导致E随着D的增加而总体下降。我们测试了这一机制，使用气体交换模型适用于叶尺度和全树CO2和H2O通量测量的桉树生长在全树室。在叶和全树尺度上都观察到E对D的峰值响应。我们发现，这种峰值响应匹配的气体交换模型，只有当T对光合作用的影响被纳入。我们的结论是，基于实地的研究E和D之间的关系需要考虑的信号，除了纯粹的水力机制，光合速率的变化。(C)2014爱思唯尔有限公司版权所有。
Leaf transpiration rate (E) frequently shows a peaked response to increasing vapour pressure deficit (D). The mechanisms for the decrease in E at high D, known as the 'apparent feed-forward response', are strongly debated but explanations to date have exclusively focused on hydraulic processes. However, stomata also respond to signals related to photosynthesis. We investigated whether the apparent feed-forward response of E to D in the field can be explained by the response of photosynthesis to temperature (T), which normally co-varies with D in field conditions. As photosynthesis decreases with increasing T past its optimum, it may drive a decrease in stomatal conductance (g(s)) that is additional to the response of g, to increasing D alone. If this additional decrease is sufficiently steep and coupling between A and gs occurs, it could cause an overall decrease in E with increasing D. We tested this mechanism using a gas exchange model applied to leaf-scale and whole-tree CO2 and H2O fluxes measured on Eucalyptus saligna growing in whole-tree chambers. A peaked response of E to D was observed at both leaf and whole-tree scales. We found that this peaked response was matched by a gas exchange model only when T effects on photosynthesis were incorporated. We conclude that field-based studies of the relationship between E and D need to consider signals related to changing photosynthetic rates in addition to purely hydraulic mechanisms. (C) 2014 Elsevier B.V. All rights reserved.