Abstract: Most previous researches of plant adaptability to environmental changes were conducted using functional traits at species level. However, one species might displayed distinct ecological strategies in different habitats. Therefore, it’s important to analyze the intraspecific variation of leaf functional traits and their plasticity for understanding the environmental adaption mechanisms and survival status of plant individuals. The present study determined the plant height, biomass and leaf functional traits such as morphological, stomatal, anatomical and chemical characters of medicinal plant Hedyotis caudatifolia from four habitats (grassland, shrub-grassland, forest edge and understory) in Mt. Dayao of Guangxi. Results showed that functional traits varied apparently among different habitats. Among all leaf functional traits, potential conductance index (PCI) exhibited the highest coefficient of variation (CV), while CV of leaf carbon content, looseness of leaf spongy tissue, spongy mesophyll thickness and leaf thickness were lower. Plasticity index (PI) ranked inconsistently with CV for some traits, i.e. potential conductance index displayed the highest PI, followed by mass-based chlorophyll content, leaf area, specific leaf area and ratio of leaf palisade to spongy mesophyll thickness, etc. Principal component analysis (PCA) indicated that the variations of leaf functional traits were closely correlated with light utilization, water conductivity and nutrient strategies, dominated by light adaptation. Analysis of Variable Importance in Projection (VIP) revealed that anatomical structure contributed to the most variances of plant height and biomass, followed by stomatal characters; chemical traits accounted for the least in the contribution rates. The changes of leaf functional traits and their syndromes of H. caudatifolia facilitated itself in utilizing natural environmental resources such as light and water. Thus, it was capable of coping with disadvantages in different habitats, and finally promoted the plant growth and biomass accumulation, which enabled its individuals to compete with other plants in the community for the further survival and reproduction. The study will provide references for the assessment of survival status and safety risk of H. caudatifolia under degraded habitats.

Key words: leaf functional traits, plant height, biomass, plasticity, habitat, adaptation

摘要： 关于植物适应环境变化的研究通常基于功能性状的物种均值，然而同一物种在不同生境中可能具有不同的适应策略。因此，探究植物功能性状的变异及可塑性对于理解物种对生境异质性的适应机制至关重要。本研究选取广西大瑶山地区4种生境(草地、灌草地、林缘及林下)下的药用植物剑叶耳草Hedyotis caudatifolia为试材，通过测定叶片形态、气孔特征和叶片解剖学性状，以及植株高度和生物量等指标，分析不同生境下剑叶耳草的叶片功能性状及其可塑性，以及这些指标对植物生长的影响。结果显示，不同生境下剑叶耳草的叶片功能性状存在差异，其中潜在气孔导度指数的变异系数最高，而叶片碳含量、叶片疏松度、海绵组织厚度、叶片厚度的变异系数相对较低。潜在气孔导度指数的可塑性指数最高，其次为单位质量叶绿素含量、叶面积、比叶面积、栅/海比等。主成分分析表明，叶片功能性状在不同生境下的变异与光能利用、水分传导和养分策略密切相关，以光适应为主导。叶片解剖性状对生物量变异的贡献率为36%，气孔特征、形态性状和化学性状的贡献率分别为24%、22%和18%。剑叶耳草叶片功能性状间的相关组合及其变化，使其能充分利用不同生境的光照、水分等资源，以应对逆境条件，维持植株生长和生物量的积累。该研究结果为剑叶耳草在生境退化状况下的生存状态和安全风险评估提供依据。

关键词: 叶片功能性状, 植株高度, 生物量, 可塑性, 生境, 适应性