中文摘要：

细根具有复杂的分支系统，以根序（root order）为取样单元的细根生理生态学研究正在成为根系生态学研究领域的重要内容。该研究以海南岛尖峰岭4个热带阔叶树种海南蕈树（Altingia obovata）、厚壳桂（Cryptocarya chinensis）、山杜英（Elaeocarpus sylvestris）和黄桐（Endospermum chinense）为研究对象，测定了1—5级细根的形态、解剖结构和组织碳（C）、氮（N）含量，旨在探讨这些根系特征之间的联系。研究表明：4个树种的细根形态差异较大，但在树种水平上直径、根长和组织密度均随着根序的升高而增加，比根长则随着根序的升高而降低；低级根（前2级根或前3级根）具有皮层组织，是典型的吸收根，而高级根皮层组织消失，是典型的运输和储藏根；影响直径大小最重要的因子是皮层厚度，它可以解释细根直径变异的97％，而维管束直径仅能解释细根直径变异的70％；根组织N和C浓度受维管束-根直径比（维根比）的影响，随着维根比增加，组织N浓度显著降低，组织C浓度显著升高。4个树种细根的C／N比的变异受组织N浓度的影响程度为76％，而受C浓度的影响程度不足10％。上述结果表明，细根的形态特征、解剖结构和组织化学含量之间存在着紧密联系，这为我们理解根系结构与功能交异提供了重要依据。

英文摘要：

Aims Knowledge of fine root morphology, anatomy and tissue chemistry is critical to understanding root functions （e.g., longevity）, but little is known about these root traits and their relationships in woody plants. We investigated root morphology, anatomy and tissue chemistry of the first five orders in four tropical tree species （Altingia obovata, Cryptocarya chinensis, Elaeocarpus sylvestris and Endospermum chinense） in Jianfengling of Hainan Island, China. Our objectives were to： 1） examine how root morphology （diameter, length, specific root length （SRL） and tissue density）, anatomy （cortex thickness and stele to root diameter ratio （V/R）） and tissue chemistry （N and C content） changes with root branch orders and 2） reveal the relationships between anatomical structures and root diameter or tissue N or C concentrations in the four tree species. Methods Tree roots of the four species were sampled in August 2009, and root samples were sorted into different orders. Root morphology of the first five orders was analyzed by the Win-RHIZO system. Root tissue C and N concentrations in roots of each order were analyzed by the Vario MACRO Element Analyzer. Individual roots in each order were made into paraffin slices stained by safranin and fast green to observe root anatomical structures and to calculate cortical thickness, stele diameter and V/R. Important findings From the first to fifth order, root diameter, length and tissue density as well as stele diameter and V/R increased, and SRL and cortex thickness decreased in all species. The first two or three orders exhibited primary development with an intact cortex and lower V/R ratio, whereas higher order roots showed secondary development with no cortex and higher V/R ratio. Correlation analysis indicated that cortex thickness can explain 97% of the variations of root diameter and 70% of stele diameter. In all species, tissue N concentration decreased and tissue C concentrations increased with ascending root order. Moreover, C/N r