Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA, 90095, USA.
Key Laboratory of Plant Resources, Institute of Botany, the Chinese Academy of Sciences, Beijing, 100093, China.
Am J Bot. 2018 Oct;105(10):1672-1687. doi: 10.1002/ajb2.1164. Epub 2018 Oct 12.
Studies across diverse species have established theory for the contribution of leaf traits to plant drought tolerance. For example, species in more arid climates tend to have smaller leaves of higher vein density, higher leaf mass per area, and more negative osmotic potential at turgor loss point (π ). However, few studies have tested these associations for species within a given lineage that have diversified across an aridity gradient.
We analyzed the anatomy and physiology of 10 Ceanothus (Rhamnaceae) species grown in a common garden for variation between and within "wet" and "dry" subgenera (Ceanothus and Cerastes, respectively) and analyzed a database for 35 species for leaf size and leaf mass per area (LMA). We used a phylogenetic generalized least squares approach to test hypothesized relationships among traits, and of traits with climatic aridity in the native range. We also tested for allometric relationships among anatomical traits.
Leaf form, anatomy, and drought tolerance varied strongly among species within and between subgenera. Cerastes species had specialized anatomy including hypodermis and encrypted stomata that may confer superior water storage and retention. The osmotic potentials at turgor loss point (π ) and full turgor (π ) showed evolutionary correlations with the aridity index (AI) and precipitation of the 10 species' native distributions, and LMA with potential evapotranspiration for the 35 species in the larger database. We found an allometric correlation between upper and lower epidermal cell wall thicknesses, but other anatomical traits diversified independently.
Leaf traits and drought tolerance evolved within and across lineages of Ceanothus consistently with climatic distributions. The π has signal to indicate the evolution of drought tolerance within small clades.
跨多种物种的研究已经建立了叶片特征对植物耐旱性贡献的理论。例如，在更干旱气候条件下的物种往往具有更小的叶片、更高的叶脉密度、更高的比叶面积和更低的膨压丧失点的渗透压（π）。然而，很少有研究在给定谱系内的物种中测试这些关联，这些物种在干旱梯度上已经多样化。
我们分析了在一个共同花园中生长的 10 种 Ceanothus（Rhamnaceae）物种的解剖结构和生理学特性，以研究“湿”和“干”亚属（分别为 Ceanothus 和 Cerastes）之间和内部的变异，并分析了一个数据库中的 35 种物种的叶大小和比叶面积（LMA）。我们使用进化广义最小二乘法方法来测试特征之间以及特征与原生范围气候干旱之间的假设关系。我们还测试了解剖特征之间的异速关系。
叶片形态、解剖结构和耐旱性在亚属内和亚属间的物种间存在很大差异。Cerastes 物种具有专门的解剖结构，包括下皮层和加密的气孔，这可能赋予其更好的储水和保水能力。膨压丧失点（π）和完全膨压（π）的渗透压与 10 个物种原生分布的干旱指数（AI）和降水量表现出进化相关性，而 35 个物种的比叶面积（LMA）与更大数据库中潜在蒸散量呈正相关。我们发现上表皮和下表皮细胞壁厚度之间存在一种异速关系，但其他解剖特征则独立多样化。
叶片特征和耐旱性在 Ceanothus 的谱系内和谱系间的进化与气候分布一致。π具有指示小分支内耐旱性进化的信号。
