Growth and phenotypic plasticity of two tropical tree species under low light availability

两种热带树种在弱光条件下的生长和表型可塑性

Aims Screening tree species in tropical rainforest according to their shade tolerance is important to efficiently manage the native trees of economic significance in secondary forest enrichment regimes.The objective of this study was to determine the whole-plant light compensation point(WPLCP)and compare the phenotypic plasticity in relation to growth and carbon allocation of Cariniana legalis and Gallesia integrifolia seedlings under low light availability.Methods Seedlings were cultivated for 77 days under conditions of five photosynthetically active radiation(PAR)(0.02,1.1,2.3,4.5 and 5.9 mol photons m^(−2)day^(−1))in three replicates.Growth and carbon allocation variables were determined.Important Findings Growth rates of C.legalis were higher and lower than those of G.integrifolia under 1.1 and 5.9 mol photons m^(−2)day^(−1),respectively.The WPLCP differed significantly between the two species.In accordance with the criteria of the shade tolerance classification for these two tropical tree species,our results showed that C.legalis had lower WPLCP and phenotypic plasticity in terms of higher growth rates and greater shade tolerance than G.integrifolia.From a practical point of view,we demonstrated that the differential linkage between growth and changing PAR between the two species can become a useful tool for comparing and selecting tree species in forest enrichment projects.

根据耐荫性筛选热带雨林树种,对于在次生林富集区域中更有效地管理具有经济意义的本土树种非常重要。本研究旨在确定全株的光补偿点,比较弱光条件下Cariniana legalis和Gallesia integrifolia幼苗生长和碳分配有关的表型可塑性。实验所用幼苗在5种光合有效辐射条件下(0.02、1.1、2.3、4.5和5.9 mol photons m^(−2)day^(−1))培养77天,设置3个重复,并分析了生长和碳分配变量指标。结果显示,在1.1 mol photons m^(−2)day^(−1)条件下,C.legalis的生长速率高于G.integrifolia,而在5.9 mol photons m^(−2)day^(−1)条件下,C.legalis的生长速率低于G.integrifolia。不同物种间的光补偿点差异显著。根据耐阴分类标准对这两种热带树种进行分类,我们的研究结果表明,C.legalis相对较低的光补偿点和表型可塑性与生长速率有关,比G.integrifolia具有更强的耐荫性。从实际的角度来看,我们证明了两种树种之间生长和光合有效辐射变化的不同关系可以成为在森林丰富工程中比较和选择种植树种的可行工具。