Department of Plant Biology, University of Georgia, 2502 Miller Plant Sciences, Athens, GA 30602, USA.
J Exp Bot. 2013 Oct;64(13):4089-99. doi: 10.1093/jxb/ert249. Epub 2013 Sep 28.
The leaf economics spectrum (LES) describes large cross-species variation in suites of leaf functional traits ranging from resource-acquisitive to resource-conservative strategies. Such strategies have been integral in explaining plant adaptation to diverse environments, and have been linked to numerous ecosystem processes. The LES has previously been found to be significantly modulated by climate, soil fertility, biogeography, growth form, and life history. One largely unexplored aspect of LES variation, whole-plant ontogeny, is investigated here using multiple populations of three very different species of sunflower: Helianthus annuus, Helianthus mollis, and Helianthus radula. Plants were grown under environmentally controlled conditions and assessed for LES and related traits at four key developmental stages, using recently matured leaves to standardize for leaf age. Nearly every trait exhibited a significant ontogenetic shift in one or more species, with trait patterns differing among populations and species. Photosynthetic rate, leaf nitrogen concentration, and leaf mass per area exhibited surprisingly large changes, spanning over two-thirds of the original cross-species LES variation and shifting from resource-acquisitive to resource-conservative strategies as the plants matured. Other traits being investigated in relation to the LES, such as leaf water content, pH, and vein density, also showed large changes. The finding that ontogenetic variation in LES strategy can be substantial leads to a recommendation of standardization by developmental stage when assessing 'species values' of labile traits for comparative approaches. Additionally, the substantial ontogenetic trait shifts seen within single individuals provide an opportunity to uncover the contribution of gene regulatory changes to variation in LES traits.
叶片经济谱（LES）描述了从资源获取到资源保守策略的一系列叶片功能特征的大范围种间变异。这些策略对于解释植物对不同环境的适应至关重要，并与许多生态系统过程有关。LES 先前被发现受到气候、土壤肥力、生物地理、生长形式和生活史的显著调节。叶片经济谱变异的一个很大程度上尚未被探索的方面，即整株植物的个体发育，在这里使用三种非常不同的向日葵物种的多个种群进行了研究：Helianthus annuus、Helianthus mollis 和 Helianthus radula。在环境控制条件下种植植物，并在四个关键发育阶段评估 LES 和相关特征，使用最近成熟的叶子来标准化叶片年龄。几乎每个特征在一个或多个物种中都表现出显著的个体发育变化，特征模式在种群和物种之间存在差异。光合速率、叶片氮浓度和叶片比叶面积表现出惊人的大变化，跨越了原始种间 LES 变异的三分之二以上，并随着植物的成熟从资源获取策略转变为资源保守策略。与 LES 相关的其他特征，如叶片含水量、pH 值和叶脉密度，也显示出很大的变化。发现 LES 策略的个体发育变异可能很大，因此在评估实验室中易变特征的“物种值”进行比较方法时，建议按发育阶段进行标准化。此外，单个个体中观察到的大量个体发育特征变化为发现 LES 特征变化中基因调控变化的贡献提供了机会。
