不同的物种对所在环境的适应性及其适应机制是生态学研究的一个重要方面，其中植物对逆境条件的适应性研究一直是生理生态学研究的热点。近日，中科院版纳植物园与美国迈阿密大学合作，在树木水力结构的研究方面取得重要进展。 研究比较了共同生长在萨王纳(savanna音译，热带稀树草原)生境的6对同属不同种树木叶片和枝条的水分关系功能特性，每对同属植物中一种是萨王纳植被的成分，另一种是邻近的河道森林植被成分。结果表明，当两类植物同样生长在干旱环境中时，大多枝条的木质部结构功能特征在两类植物间没有显著差异，而多数叶片的水分相关的特征在两类植物间差异显著。与森林成分植物相比，萨王纳种对干旱适应的优势主要与叶片而非枝条的结构功能特征相关。统计分析还表明属间差异是植物许多功能特性差异的主要原因，说明尽管萨王纳和森林生境的选择压力差别很大，植物的系统发育对其大多数水力结构特征的发育比生境具更重要的影响，揭示了植物系统发育上的惰性。研究结果在生态学重要期刊《生态学》（Oecologia(2008，155：405-415)）上发表。
萨王纳和热带季雨林同样生长在具有周期性干湿季节交替的热带地区，其旱季往往比热带季雨林更加干燥而漫长的。由于旱季水分不足，树木分布稀疏，树木之间的距离通常是其高度的5-10倍；植株对于水分的获得和应用尤为重要，其叶片功能的维持和水分往往具有密切的关系，漫长的旱季使一些树木具有储存水分的能力，许多具有独特的水分适应策略。（来源：中科院西双版纳热带植物园）
生物谷推荐原始出处：
（Oecologia），10.1007/s00442-007-0918-5，Guang-You Hao, Guillermo Goldstein
Stem and leaf hydraulics of congeneric tree species from adjacent tropical savanna and forest ecosystems
Guang-You Hao1, 2, William A. Hoffmann3, Fabian G. Scholz4, Sandra J. Bucci4, Frederick C. Meinzer5, Augusto C. Franco6, Kun-Fang Cao1 and Guillermo Goldstein2, 7
(1) Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun, 666303 Mengla, Yunnan Province, China
(2) Department of Biology, University of Miami, Coral Gables, FL 33124, USA
(3) Department of Plant Biology, North Carolina State University, Raleigh, NC 27695-7612, USA
(4) Consejo Nacional de Investigaciones Cientificas y Técnicas (CONICET), Departamento de Biología, Universidad Nacional de la Patagonia San Juan Bosco, 9000 Comodoro Rivadavia, Argentina
(5) USDA Forest Service, Forestry Sciences Laboratory, 3200 SW Jefferson Way, Corvallis, OR 97331, USA
(6) Departamento de Botanica, Universidade de Brasilia, Caixa Postal 04457, Brasilia, DF, 70904970, Brazil
(7) Laboratorio de Ecología Funcional, Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria Nuñez, Buenos Aires, Argentina
Communicated by Ram Oren.
Abstract Leaf and stem functional traits related to plant water relations were studied for six congeneric species pairs, each composed of one tree species typical of savanna habitats and another typical of adjacent forest habitats, to determine whether there were intrinsic differences in plant hydraulics between these two functional types. Only individuals growing in savanna habitats were studied. Most stem traits, including wood density, the xylem water potential at 50% loss of hydraulic conductivity, sapwood area specific conductivity, and leaf area specific conductivity did not differ significantly between savanna and forest species. However, maximum leaf hydraulic conductance (K leaf) and leaf capacitance tended to be higher in savanna species. Predawn leaf water potential and leaf mass per area were also higher in savanna species in all congeneric pairs. Hydraulic vulnerability curves of stems and leaves indicated that leaves were more vulnerable to drought-induced cavitation than terminal branches regardless of genus. The midday K leaf values estimated from leaf vulnerability curves were very low implying that daily embolism repair may occur in leaves. An electric circuit analog model predicted that, compared to forest species, savanna species took longer for their leaf water potentials to drop from predawn values to values corresponding to 50% loss of K leaf or to the turgor loss points, suggesting that savanna species were more buffered from changes in leaf water potential. The results of this study suggest that the relative success of savanna over forest species in savanna is related in part to their ability to cope with drought, which is determined more by leaf than by stem hydraulic traits. Variation among genera accounted for a large proportion of the total variance in most traits, which indicates that, despite different selective pressures in savanna and forest habitats, phylogeny has a stronger effect than habitat in determining most hydraulic traits.
