Atmospheric chemists have historically treated leaves as inert surfaces that merely emit volatile hydrocarbons. However, a growing body of evidence suggests that leaves are ubiquitous substrates for multiphase reactions–implying the presence of chemicals on their surfaces. This Review provides an overview of the chemistry and reactivity of the leaf surface’s “chemical landscape”, the dynamic ensemble of compounds covering plant leaves. We classified chemicals as endogenous (originating from the plant and its biome) or exogenous (delivered from the environment), highlighting the biological, geographical, and meteorological factors driving their contributions. Based on available data, we predicted ≫2 μg cm^–2 of organics on a typical leaf, leading to a global estimate of ≫3 Tg for multiphase reactions. Our work also highlighted three major knowledge gaps: (i) the overlooked role of ambient water in enabling the leaching of endogenous substances and mediating aqueous chemistry; (ii) the importance of phyllosphere biofilms in shaping leaf surface chemistry and reactivity; (iii) the paucity of studies on the multiphase reactivity of atmospheric oxidants with leaf-adsorbed chemicals. Although biased toward available data, we hope this Review will spark a renewed interest in the leaf surface’s chemical landscape and encourage multidisciplinary collaborations to move the field forward.

中文翻译：

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叶表面的化学景观及其与大气的相互作用

大气化学家历来将叶子视为惰性表面，仅释放挥发性碳氢化合物。然而，越来越多的证据表明，叶子是多相反应普遍存在的基质，这意味着叶子表面存在化学物质。本综述概述了叶子表面“化学景观”的化学和反应性，即覆盖植物叶子的化合物的动态整体。我们将化学物质分为内源性（源自植物及其生物群落）或外源性（来自环境），强调了推动其贡献的生物、地理和气象因素。根据现有数据，我们预测典型叶子上的有机物含量≥2 μg cm ^–2，从而对多相反应的总体估计值≥3 Tg。我们的工作还强调了三个主要的知识差距：（i）环境水在实现内源性物质浸出和介导水化学方面的作用被忽视； (ii) 叶际生物膜在塑造叶子表面化学和反应性方面的重要性； (iii) 缺乏关于大气氧化剂与叶子吸附的化学物质的多相反应性的研究。尽管偏向于现有数据，但我们希望这篇综述能够激发人们对叶表面化学景观的新兴趣，并鼓励多学科合作来推动该领域的发展。