Departments of Biology and Environmental Science, Whittier College, Whittier, California.
Department of Botany and Plant Sciences, University of California Riverside, Riverside, California.
Plant Cell Environ. 2018 Nov;41(11):2617-2626. doi: 10.1111/pce.13367. Epub 2018 Aug 7.
Isohydry (maintenance of plant water potential at the cost of carbon gain) and anisohydry (gas exchange maintenance at the cost of declining plant water status) make up two ends of a stomatal drought response strategy continuum. However, few studies have merged measures of stomatal regulation with xylem hydraulic safety strategies based on in situ field measurements. The goal of this study was to characterize the stomatal and xylem hydraulic safety strategies of woody species in the biodiverse Mediterranean-type ecosystem region of California. Measurements were conducted in situ when California was experiencing the most severe drought conditions in the past 1,200 years. We found coordination among stomatal, hydraulic, and standard leaf functional traits. For example, stem xylem vulnerability to cavitation (P ) was correlated with the water potential at stomatal closure (P ); more resistant species had a more negative water potential at stomatal closure. The degree of isohydry-anisohydry, defined at P -P , was correlated with the hydraulic safety margin across species; more isohydric species had a larger hydraulic safety margin. In addition, we report for the first time P values below -10 MPa. Measuring these traits in a biodiverse region under exceptional drought conditions contributes to our understanding of plant drought responses.
等水合作用（以碳获取为代价维持植物水势）和不等水合作用（以植物水分状况下降为代价维持气体交换）构成了气孔干旱响应策略连续体的两个极端。然而，很少有研究将气孔调节措施与基于原位田间测量的木质部水力安全策略结合起来。本研究的目的是描述加利福尼亚生物多样性地中海型生态系统地区木本物种的气孔和木质部水力安全策略。当加利福尼亚经历过去 1200 年来最严重的干旱条件时，我们在现场进行了测量。我们发现了气孔、水力和标准叶片功能特性之间的协调。例如，木质部对空化的脆弱性（P ）与气孔关闭时的水势（P ）相关；更具抗性的物种在气孔关闭时具有更负的水势。在 P -P 定义的等水合作用-不等水合作用程度与跨物种的水力安全裕度相关；更等水合作用的物种具有更大的水力安全裕度。此外，我们首次报告了低于-10 MPa 的 P 值。在异常干旱条件下的生物多样性地区测量这些特征有助于我们了解植物的干旱响应。
