Summary Co‐occurring plants show wide variation in their hydraulic and photosynthetic traits. Here, we extended ‘least‐cost’ optimality theory to derive predictions for how variation in key hydraulic traits potentially affects the cost of acquiring and using water in photosynthesis and how this, in turn, should drive variation in photosynthetic traits. We tested these ideas across 18 woody species at a temperate woodland in eastern Australia, focusing on hydraulic traits representing different aspects of plant water balance, that is storage (sapwood capacitance, CS), demand vs supply (branch leaf : sapwood area ratio, AL : AS and leaf : sapwood mass ratio and ML : MS), access to soil water (proxied by predawn leaf water potential, ΨPD) and physical strength (sapwood density, WD). Species with higher AL : AS had higher ratio of leaf‐internal to ambient CO2 concentration during photosynthesis (ci : ca), a trait central to the least‐cost theory framework. CS and the daily operating range of tissue water potential (∆Ψ) had an interactive effect on ci : ca. CS, WD and ΨPD were significantly correlated with each other. These results, along with those from multivariate analyses, underscored the pivotal role leaf : sapwood allocation (AL : AS), and water storage (CS) play in coordination between plant hydraulic and photosynthetic systems. This study uniquely explored the role of hydraulic traits in predicting species‐specific photosynthetic variation based on optimality theory and highlights important mechanistic links within the plant carbon–water balance.

中文翻译：

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共生木本植物水力与光合性状协调的理论与试验


摘要 共生植物在水力和光合特性方面表现出很大的差异。在这里，我们扩展了“最小成本”最优理论，以得出关于关键水力性状的变化如何潜在影响光合作用中获取和使用水的成本的预测，以及这反过来又如何驱动光合性状的变化。我们在澳大利亚东部温带林地的 18 个木本物种中测试了这些想法，重点关注代表植物水平衡不同方面的水力特征，即储存（边材电容，CS）、需求与供应（枝叶：边材面积比，AL） ：AS 和叶：边材质量比和 ML：MS）、土壤水的获取（由黎明前叶水势，ΨPD 代表）和物理强度（边材密度，WD）。具有较高 AL : AS 的物种在光合作用过程中叶内二氧化碳浓度与环境二氧化碳浓度之比较高 (ci : ca)，这是最低成本理论框架的核心特征。 CS 和组织水势 (ΔΨ) 的每日运行范围对 ci : ca 具有交互作用。 CS、WD 和 ΨPD 彼此显着相关。这些结果以及多变量分析的结果强调了叶子的关键作用：边材分配（AL：AS）和水储存（CS）在植物水力和光合作用系统之间的协调中发挥着重要作用。这项研究基于最优理论独特地探讨了水力性状在预测物种特异性光合变异中的作用，并强调了植物碳水平衡中的重要机制联系。