Leaf anatomy plasticity of Alchornea triplinervia (Euphorbiaceae) under distinct light regimes in a Brazilian montane Atlantic rain forest |
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Authors: | Giselle Rôças Cláudia Franca Barros Fábio Rubio Scarano |
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Institution: | Universidade Federal do Rio de Janeiro, Departamento de Ecologia, IB, CCS, Ilha do Fund?o, Caixa postal 68020; 21941-590, Rio de Janeiro, RJ, Brazil, BR Jardim Botanico do Rio de Janeiro, Laboratório de Botanica Estrutural, 22460-030, Rio de Janeiro, RJ, Brazil, BR
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Abstract: | Alchornea triplinervia trees occur in a montane Atlantic rainforest at the Macaé de Cima State Ecological Reserve (Nova Friburgo, RJ, Brazil). They
are found in two adjacent secondary forests at distinct successional stages: a late-secondary (shaded and humid) and an early-secondary
forest (drier, higher light intensities reaching the understory). Leaf samples collected in these environments were compared
in regard to various anatomic parameters. Histochemical tests, anatomic measurements and counting indicated no significant
variation for the basic leaf anatomy. Nevertheless, as compared to the late-secondary forest, the leaves of the early-secondary
forest individuals showed an increased bulk of sclerenchyma at the main nervation and petiole, gelatinous fibers with hygroscopic
walls all along the central vascular system, thicker cuticle, a higher abaxial stomatal density, abundance of tannin in the
mesophyll, a significantly thicker palisade and spongy parenchyma, and compactation of the spongy parenchyma. This anatomical
variation indicates an increased xeromorphism of leaves under the drier conditions of the early-secondary forest. Leaf anatomy
plasticity may contribute to the high ecological plasticity of this widespread neotropical species.
Received: 11 November 1996 / Accepted: 5 February 1997 |
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Keywords: | Alchornea triplinervia Atlantic rain forest Leaf anatomy Phenotypic plasticity |
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