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Leaf structural diversity is related to hydraulic capacity in tropical rain forest trees

Sack, Lawren, Frole, Kristen
Ecology 2006 v.87 no.2 pp. 483-491
tropical rain forests, forest trees, leaves, plant anatomy, traits, shade tolerance, Panama
The hydraulic resistance of the leaf (Rₗ) 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 Rₗ varied by an order of magnitude across 10 tree species of Panamanian tropical lowland rain forest. Here, correlations were tested between Rₗ and 24 traits relating to leaf venation and mesophyll structure, and to gross leaf form. Across species, Rₗ was related to both venation architecture and mesophyll structure. Rₗ was positively related to the theoretical axial resistivity of the midrib, determined from xylem conduit numbers and dimensions, and Rₗ was negatively related to venation density in nine of 10 species. Rₗ 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 Rₗ, 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 Rₗ‐linked and Rₗ‐independent traits related strongly to regeneration irradiance, indicating the potential importance of both types of traits in establishment ecology.