Data from: Stronger cooling effects of transpiration and morphology of the plants from a hot dry habitat than from a hot wet habitat

1. Leaf temperature exerts an important impact on the microenvironment and physiological processes of leaves. Plants from different habitats have different strategies to regulate leaf temperature. The relative importance of morphology and transpiration for leaf temperature regulation in the hot habitat is still unclear. 2. We investigated 22 leaf morphological traits, transpiration, and thermal properties of 38 canopy species of seedlings in a greenhouse, including 18 dominant species from a hot wet habitat (HW) and 20 dominant species from a hot dry habitat (HD). To separate the impact of transpiration and morphology on leaf temperature, we measured the diurnal courses of leaf temperatures with and without transpiration. The temperature of a reference leaf beside each individual was measured simultaneously to render temperatures comparable. 3. Generally, the species from HD showed lower leaf temperatures than the species from HW under the same conditions. Both transpiration capacity and cooling effect of leaf morphology were stronger for the plants from HD. Active transpiration provides a suitable thermal environment for photosynthesis, while xeromorphic leaves can dampen heat stress when transpiration is suppressed. Higher vein density and stomatal pore area index (SPI) facilitated higher transpiration capacity of the plants from HD. Meanwhile, shorter leaves and thinner lower epidermis of the plants from HD were more efficient in heat transfer, although relationships were much weaker than the synergic effect of all the morphologic traits. 4. Our results confirmed that transpiration and leaf morphology provided double insurance for avoiding overheating, particularly for plant from HD. We emphasize that transpiration is a more effective way to cool leaves than morphology when water is sufficient, which may be an important adaptation for plant from HD where rainfall is sporadic. Our results provide further insight into the relationship between morphology and transpiration for the regulation of leaf temperature, and the co-evolution of gas exchange and thermal regulation of leaves.

1. 叶片温度（Leaf temperature）对叶片微环境及生理过程具有重要调控作用。不同生境下的植物具备各异的叶片温度调控策略。然而，热生境中叶片形态与蒸腾作用在叶片温度调控中的相对重要性仍未明确。
2. 我们于温室环境中针对38种冠层幼苗开展研究，测定了22项叶片形态性状、蒸腾特性与热学属性；其中包含18种来自湿热生境（hot wet habitat, HW）的优势物种，以及20种来自干热生境（hot dry habitat, HD）的优势物种。为厘清蒸腾作用与叶片形态对叶片温度的独立影响，我们分别测定了存在蒸腾作用与抑制蒸腾作用时的叶片日间温度变化过程。同时，对每株植株旁的参照叶片同步进行温度测定，以保证不同样本间的温度数据具备可比性。
3. 整体而言，在相同实验条件下，干热生境来源的物种其叶片温度显著低于湿热生境来源的物种。干热生境物种的蒸腾能力与叶片形态的降温效应均更强。主动蒸腾作用可为光合作用提供适宜的热环境，而在蒸腾作用受抑制时，旱生形态叶片可缓解热胁迫。干热生境物种拥有更高的叶脉密度与气孔孔隙面积指数（stomatal pore area index, SPI），这提升了其蒸腾能力。同时，干热生境物种的叶片更短、下表皮更薄，热传递效率更高，尽管该类单一性状的关联强度远弱于所有形态性状的协同效应。
4. 本研究结果证实，蒸腾作用与叶片形态可为叶片避免过热提供双重保障，这一点在干热生境来源的物种中尤为显著。我们强调，在水分充足的条件下，蒸腾作用相比叶片形态是更为高效的叶片降温途径，这可能是干热生境物种对零星降雨生境的重要适应策略。本研究结果进一步阐明了叶片温度调控中形态与蒸腾作用的关联机制，以及叶片气体交换与热调控的协同进化关系。