Data from: Light and growth form interact to shape stomatal ratio among British angiosperms

In most plants, stomata are located only on the abaxial leaf surface (hypostomy), but many plants have stomata on both surfaces (amphistomy). High light and herbaceous growth form have been hypothesized to favor amphistomy, but these hypotheses have not been rigorously tested together using phylogenetic comparative methods.
I leveraged a large dataset including stomatal ratio, Ellenberg light indicator value, growth form and phylogenetic relationships for 372 species of British angiosperms. I used phylogenetic comparative methods to test how light and/or growth form influence stomatal ratio and density.
High light and herbaceous growth form are correlated with amphistomy, as predicted, but they also interact; the effect of light is pronounced in therophytes (annuals) and perennial herbs, but muted in phanerophytes (shrubs and trees). Furthermore, amphistomy and stomatal density evolve together in response to light.
Comparative analyses of British angiosperms reveal two major insights. First, light and growth form interact to shape stomatal ratio; amphistomy is common under high light, but mostly for herbs. Second, coordinated evolution of adaxial stomatal density and light tolerance indicates that amphistomy helps to optimally balance light acquisition with gas exchange. Stomatal ratio may have potential as a functional trait for paleoecology and crop improvement.

绝大多数植物的气孔仅分布于叶远轴面，该分布模式被称为单气孔型（hypostomy）；但不少植物的叶片两面均分布有气孔，该模式被称为双气孔型（amphistomy）。此前已有假说提出，高光环境与草本生长型更易演化出双气孔型，但这类假说尚未通过系统发育比较分析法（phylogenetic comparative methods）开展联合严格验证。
本研究依托涵盖372种英国被子植物的大型数据集，该数据集包含气孔比率（stomatal ratio）、埃伦贝格光指示值（Ellenberg light indicator value）、生长型以及系统发育关系四类核心信息。研究采用系统发育比较分析法，检验光照条件与/或生长型对气孔比率及气孔密度（stomatal density）的调控效应。
研究结果与假说预测一致：高光环境与草本生长型均与双气孔型呈显著相关，且二者存在交互作用；光照对气孔分布模式的影响在一年生植物（therophytes）与多年生草本中表现显著，但在高位芽植物（phanerophytes，即灌木与乔木）中则被弱化。此外，双气孔型与气孔密度会响应光照而协同演化。
针对英国被子植物的比较分析得到两项核心认知：其一，光照与生长型共同塑造气孔比率，双气孔型在高光环境下更为常见，但主要分布于草本类群；其二，近轴面（adaxial leaf surface）气孔密度与耐光性的协同演化表明，双气孔型有助于在光捕获与气体交换之间实现最优平衡。气孔比率有望成为古生态学与作物改良研究中的功能性状。