The viability of forest trees, in response to climate change-associated drought, will depend on their capacity to survive through genetic adaptation and phenotypic plasticity in drought tolerance traits. Genotypes with enhanced plasticity for drought tolerance (adaptive plasticity) will have a greater ability to persist and delay the onset of hydraulic failure. By examining populations from different climate-origins grown under contrasting soil water availability, we tested for genotype (G), environment (E), and genotype-by-environment (G × E) effects on traits that determine the time it takes for saplings to desiccate from stomatal closure to 88% loss of stem hydraulic conductance (time to hydraulic failure, THF). Specifically, we hypothesized that: 1) THF is dependent on a G × E interaction, with longer THF for warm, dry climate populations in response to chronic water deficit treatment compared to cool, wet populations, and 2) hydraulic and allometric traits explain the observed patterns in THF. Corymbia calophylla saplings from two populations originating from contrasting climates (warm-dry or cool-wet) were grown under well-watered and chronic soil water deficit treatments in large containers. Hydraulic and allometric traits were measured and then saplings were dried-down to critical levels of drought stress to estimate THF. Significant plasticity was detected in the warm-dry population in response to water-deficit, with enhanced drought tolerance compared to the cool-wet population. Projected leaf area and total plant water storage showed treatment variation and minimum conductance showed significant population differences driving longer THF in trees from warm-dry origins grown in water-limited conditions. Our findings contribute information on intraspecific variation in key drought traits, including hydraulic and allometric determinants of THF. It highlights the need to quantify adaptive capacity in populations of forest trees in climate change-type drought to improve predictions of forest die-back.

中文翻译：

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植物性状的适应性可塑性增加了基础树在干旱下发生水力衰竭的时间

林木的生存能力，以应对气候变化相关的干旱，将取决于它们通过遗传适应和耐旱性状的表型可塑性生存的能力。具有增强的耐旱可塑性（适应性可塑性）的基因型将具有更强的持久性和延迟水力衰竭发生的能力。通过检查在对比土壤水分可用性下生长的来自不同气候来源的种群，我们测试了基因型 (G)、环境 (E) 和环境基因型 (G × E) 对决定树苗所需时间的性状的影响从气孔关闭干燥到茎导水性损失 88%（水力失效时间，THF）。具体来说，我们假设：1）THF 取决于 G × E 相互作用，较长的 THF 表示温暖，芋头来自不同气候（温暖干燥或凉爽湿润）的两个种群的树苗在大容器中在水分充足和长期土壤缺水处理下生长。测量水力和异速生长特性，然后将树苗干燥至干旱胁迫的临界水平以估计 THF。在应对缺水的暖干人群中检测到显着的可塑性，与冷湿人群相比具有增强的耐旱性。预计的叶面积和总植物蓄水量显示出处理变化，最小电导显示显着的种群差异，在水受限条件下生长的温暖干燥起源的树木中驱动更长的 THF。我们的研究结果提供了有关关键干旱性状的种内变异的信息，包括 THF 的水力和异速生长决定因素。