叶脉结构与功能及其对叶片经济谱的影响

叶脉由贯穿于叶肉内部的维管组织及其外围机械组织构成, 多样化的脉序及网络结构使叶脉系统发生变异和功能分化。该文综述了叶脉系统结构与功能的最新研究进展。通过聚焦叶脉分级系统的结构与功能及其在叶片经济谱(LES)中的重要性, 解释叶脉性状与其它叶片功能性状之间的关系及机制。不同等级叶脉在机械支撑与水分运输方面存在功能分化, 其中1-3级粗脉在维持叶片形状和叶表面积以及物理支撑方面发挥重要作用, 有利于维持叶片最大受光面积; 4级及以上细脉具有水分调节功能, 它们与气孔相互协调, 影响叶片水分运输、蒸腾散热和光合作用速率。叶片生长过程与叶脉发育的动态变化模式决定叶脉密度, 并影响叶脉密度与叶片大小之间的关系: 叶面积与粗脉密度呈显著负相关, 与粗脉直径呈显著正相关, 而与细脉密度无关。与叶脉性状相关的叶片经济谱框架模型预测, 叶脉密度较高的叶片寿命短、比叶重较小, 叶片最大碳同化速率、代谢速率以及资源获取策略潜力较高。

The Structure and Function of Leaf Veins and Their Influence on Leaf Economic Spectrum

Vascular tissues inside the mesophyll and peripheral mechanical tissues constitute the veins. The diverse orders and network structures of veins contribute to their functional diversification and differentiation. In this review, we summarized the research progresses on the structure and function of the leaf vein system. We reviewed three aspects of veins and critically evaluated the characteristics of the leaf vein hierarchy system and its important role in leaf economic spectrum (LES), and explained the mechanisms linking vein traits and other functional traits of the leaf. Leaf veins of different orders show obvious functional differentiation in terms of hydraulic conduction and mechanical support. Among them, the first three orders of veins (major veins) play a major role in maintaining leaf shape, leaf surface area and physical support, and which is conductive to the growth of leaves with the largest light-receiving area. The higher order veins (minor veins) have the function of water regulation, and their coordination with the stomata determines the rate of leaf water transport, transpiration and photosynthesis. The patterns of dynamic variation in leaf spread and leaf vein development explain the relationship between vein density and leaf size. Leaf surface area is negatively correlated with the density of main veins and positively correlated with the diameter of main veins, but independent of the density of minor veins. The framework model of LES linking with vein traits predicts that leaves with higher vein density have short lifespan and smaller leaf mass per area, which explains the better leaf carbon assimilation rate, metabolism rate and resource acquisition strategy with higher leaf vein density.