School of Biological Sciences, University of Utah, Salt Lake City, UT, 84112, USA.
Department of Biology, Indiana University, Bloomington, IN, 47405, USA.
New Phytol. 2019 Jun;222(4):1862-1872. doi: 10.1111/nph.15699. Epub 2019 Feb 17.
The isohydry-anisohydry spectrum has become a popular way to characterize plant drought responses and recovery processes. Despite the proven utility of this framework for understanding the interconnected physiological changes plants undergo in response to water stress, new challenges have arisen pertaining to the traits and tradeoffs that underlie this concept. To test the utility of this framework for understanding hydraulic traits, drought physiology and recovery, we applied a 6 wk experimental soil moisture reduction to seven tree species followed by a 6 wk recovery period. Throughout, we measured hydraulic traits and monitored changes in gas exchange, leaf water potential, and hydraulic conductivity. Species' hydraulic traits were not coordinated, as some anisohydric species had surprisingly low resistance to embolism (P ) and negative safety margins. In addition to widespread hydraulic damage, these species also experienced reductions in photosynthesis and stem water potential during water stress, and delayed recovery time. Given that we observed no benefit of being anisohydric either during or after drought, our results indicate the need to reconsider the traits and tradeoffs that underlie anisohydric behavior, and to consider the environmental, biological and edaphic processes that could allow this strategy to flourish in forests.
等水合-非等水合谱已成为一种描述植物干旱响应和恢复过程的流行方法。尽管该框架已被证明可用于理解植物对水分胁迫所经历的相互关联的生理变化，但与该概念相关的特征和权衡也出现了新的挑战。为了检验该框架在理解水力特征、干旱生理学和恢复方面的效用，我们对七种树种进行了 6 周的实验土壤水分减少处理，随后进行了 6 周的恢复期。在整个过程中，我们测量了水力特征，并监测了气体交换、叶片水势和导水率的变化。物种的水力特征并不协调，因为一些非等水合物种对栓塞的抵抗力（P）和负安全裕度令人惊讶地低。除了广泛的水力损伤外，这些物种在水分胁迫期间和之后还经历了光合作用和茎水势的减少，以及恢复时间的延迟。鉴于我们在干旱期间或之后都没有观察到非等水合的任何好处，我们的结果表明，有必要重新考虑非等水合行为的特征和权衡，并考虑可能使这种策略在森林中蓬勃发展的环境、生物和土壤过程。
