Mason Chase M, Donovan Lisa A
Department of Plant Biology, University of Georgia, Athens, GA, USA,
Oecologia. 2015 Apr;177(4):1053-66. doi: 10.1007/s00442-014-3177-2. Epub 2014 Dec 6.
Leaf defenses have long been studied in the context of plant growth rate, resource availability, and optimal investment theory. Likewise, one of the central modern paradigms of plant ecophysiology, the leaf economics spectrum (LES), has been extensively studied in the context of these factors across ecological scales ranging from global species data sets to temporal shifts within individuals. Despite strong physiological links between LES strategy and leaf defenses in structure, function, and resource investment, the relationship between these trait classes has not been well explored. This study investigates the relationship between leaf defenses and LES strategy across whole-plant ontogeny in three diverse Helianthus species known to exhibit dramatic ontogenetic shifts in LES strategy, focusing primarily on physical and quantitative chemical defenses. Plants were grown under controlled environmental conditions and sampled for LES and defense traits at four ontogenetic stages. Defenses were found to shift strongly with ontogeny, and to correlate strongly with LES strategy. More advanced ontogenetic stages with more conservative LES strategy leaves had higher tannin activity and toughness in all species, and higher leaf dry matter content in two of three species. Modeling results in two species support the conclusion that changes in defenses drive changes in LES strategy through ontogeny, and in one species that changes in defenses and LES strategy are likely independently driven by ontogeny. Results of this study support the hypothesis that leaf-level allocation to defenses might be an important determinant of leaf economic traits, where high investment in defenses drives a conservative LES strategy.
长期以来，人们一直在植物生长速率、资源可用性和最优投资理论的背景下研究叶片防御。同样，植物生态生理学的核心现代范式之一——叶片经济谱（LES），也已在从全球物种数据集到个体内部时间变化等不同生态尺度的这些因素背景下得到广泛研究。尽管LES策略与叶片防御在结构、功能和资源投资方面存在紧密的生理联系，但这些性状类别之间的关系尚未得到充分探索。本研究调查了三种不同向日葵物种在整个植物个体发育过程中叶片防御与LES策略之间的关系，这三种向日葵已知在LES策略上表现出显著的个体发育变化，主要关注物理防御和定量化学防御。植物在受控环境条件下生长，并在四个个体发育阶段对LES和防御性状进行采样。结果发现，防御随着个体发育而强烈变化，并与LES策略密切相关。在所有物种中，具有更保守LES策略叶片的更高级个体发育阶段具有更高的单宁活性和韧性，在三个物种中的两个物种中具有更高的叶片干物质含量。对两个物种的建模结果支持这样的结论，即防御的变化通过个体发育驱动LES策略的变化，而在一个物种中，防御和LES策略的变化可能由个体发育独立驱动。本研究结果支持这样的假设，即叶片水平上对防御的分配可能是叶片经济性状的一个重要决定因素，其中对防御的高投资驱动了保守的LES策略。
