Sack Lawren, Frole Kristen
Department of Botany, University of Hawai'i at Mănoa, Honolulu 96822, USA.
Ecology. 2006 Feb;87(2):483-91. doi: 10.1890/05-0710.
The hydraulic resistance of the leaf (R1) is a major bottleneck in the whole plant water transport pathway and may thus be linked with the enormous variation in leaf structure and function among tropical rain forest trees. A previous study found that R1 varied by an order of magnitude across 10 tree species of Panamanian tropical lowland rain forest. Here, correlations were tested between R1 and 24 traits relating to leaf venation and mesophyll structure, and to gross leaf form. Across species, R1 was related to both venation architecture and mesophyll structure. R1 was positively related to the theoretical axial resistivity of the midrib, determined from xylem conduit numbers and dimensions, and R1 was negatively related to venation density in nine of 10 species. R1 was also negatively related to both palisade mesophyll thickness and to the ratio of palisade to spongy mesophyll. By contrast, numerous leaf traits were independent of R1, including area, shape, thickness, and density, demonstrating that leaves can be diverse in gross structure without intrinsic trade-offs in hydraulic capacity. Variation in both R1-linked and R1-independent traits related strongly to regeneration irradiance, indicating the potential importance of both types of traits in establishment ecology.
叶片的水力阻力（R1）是整个植物水分运输途径中的一个主要瓶颈，因此可能与热带雨林树木叶片结构和功能的巨大差异有关。先前的一项研究发现，巴拿马热带低地雨林的10种树木的R1相差一个数量级。在此，对R1与24个与叶脉、叶肉结构以及叶片整体形态有关的性状之间的相关性进行了测试。在不同物种间，R1与叶脉结构和叶肉结构均相关。R1与根据木质部导管数量和尺寸确定的中脉理论轴向电阻率呈正相关，并且在10个物种中有9个物种的R1与叶脉密度呈负相关。R1还与栅栏叶肉厚度以及栅栏叶肉与海绵叶肉的比例均呈负相关。相比之下，许多叶片性状与R1无关，包括面积、形状、厚度和密度，这表明叶片在整体结构上可以多种多样，而在水力容量方面不存在内在权衡。与R1相关和与R1无关的性状变异都与再生光照强度密切相关，这表明这两种类型的性状在定居生态学中都具有潜在的重要性。
