不同的物種對(duì)所在環(huán)境的適應(yīng)性及其適應(yīng)機(jī)制是生態(tài)學(xué)研究的一個(gè)重要方面,，其中植物對(duì)逆境條件的適應(yīng)性研究一直是生理生態(tài)學(xué)研究的熱點(diǎn)。近日,，中科院版納植物園與美國邁阿密大學(xué)合作,，在樹木水力結(jié)構(gòu)的研究方面取得重要進(jìn)展,。 研究比較了共同生長在薩王納(savanna音譯，熱帶稀樹草原)生境的6對(duì)同屬不同種樹木葉片和枝條的水分關(guān)系功能特性,，每對(duì)同屬植物中一種是薩王納植被的成分,，另一種是鄰近的河道森林植被成分。結(jié)果表明,，當(dāng)兩類植物同樣生長在干旱環(huán)境中時(shí),，大多枝條的木質(zhì)部結(jié)構(gòu)功能特征在兩類植物間沒有顯著差異，而多數(shù)葉片的水分相關(guān)的特征在兩類植物間差異顯著,。與森林成分植物相比,，薩王納種對(duì)干旱適應(yīng)的優(yōu)勢主要與葉片而非枝條的結(jié)構(gòu)功能特征相關(guān)。統(tǒng)計(jì)分析還表明屬間差異是植物許多功能特性差異的主要原因,，說明盡管薩王納和森林生境的選擇壓力差別很大,，植物的系統(tǒng)發(fā)育對(duì)其大多數(shù)水力結(jié)構(gòu)特征的發(fā)育比生境具更重要的影響，揭示了植物系統(tǒng)發(fā)育上的惰性,。研究結(jié)果在生態(tài)學(xué)重要期刊《生態(tài)學(xué)》（Oecologia(2008,，155：405-415)）上發(fā)表。
薩王納和熱帶季雨林同樣生長在具有周期性干濕季節(jié)交替的熱帶地區(qū),，其旱季往往比熱帶季雨林更加干燥而漫長的,。由于旱季水分不足，樹木分布稀疏,，樹木之間的距離通常是其高度的5-10倍,；植株對(duì)于水分的獲得和應(yīng)用尤為重要，其葉片功能的維持和水分往往具有密切的關(guān)系,，漫長的旱季使一些樹木具有儲(chǔ)存水分的能力,，許多具有獨(dú)特的水分適應(yīng)策略。（來源：中科院西雙版納熱帶植物園）
生物谷推薦原始出處：
（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.
