Caracterização dos atributos foliares de espécies lenhosas em remanescente de Floresta Atlântica do Estado do Rio de Janeiro

Abstract

The woody species are distributed in strata in the Atlantic Forest and, due to the architecture of their canopies, different luminosity conditions are provided for leaves from the same individual. The results of light distribution at different levels may reflect into a variation in morpho-anatomical characters. The high diversity of forest species creates knowledge gaps about establishment, reproduction, physiology and defense systems of these plants. Thus, the present study aims to characterize the morpho-anatomical parameters of shade and sun leaves of woody species, in order to identify correlations among leaf attributes in response to variations in light intensity. To carry out the research, individuals belonging to the Euphorbiaceae, Erythroxylaceae and Lauraceae families occurring in the Municipal Natural Park of Curió de Paracambi, RJ, an urban park with a remnant of the Submontane Dense Ombrophilous Forest, were selected. Fully expanded leaves were collected from branches located at the canopy and under the canopy, of different individuals from the following species: Actinostemon verticillatus (Klotzsch) Baill., Senefeldera verticillata (Vell) Croizat, Erythroxylum pulchrum A.St.-Hil. and Urbanodendron verrucosum (Nees) Mez. After collection, the plant material was fixed and processed according to usual methods for morphoanatomy and ultrastructure studies. Anatomical parameters were measured on two leaves of each individual. The statistical analyzes of this work include parametric and non-parametric tests, and correlation matrices among the evaluated attributes. Histochemical tests revealed the presence of special metabolites of the classes of terpenes and phenolic substances, in the entire leaf blade, in species from the three families. After morphological analysis, it was observed that sun leaves of A. verticillatus and U. verrucosum presented higher leaf mass per unit area and thickness, and lower specific leaf area in relation to the shade leaves. Among anatomical attributes, stomatal frequency, stomatal pores and stomatal conductance were higher in shade leaves of A. verticillatus, E. pulchrum and U. verrucosum. Differently, their sun leaves presented greater palisade parenchyma height. The venation pattern was the common camptobrochidodromous type, although vascular terminations and ramifications varied among species. Leaf sheath extensions showed greater height in the heterobaric-type Urbanodendron verrucosum leaves, while the semi-heterobaric-type of E. pulchrum, greater width. Sun and shade leaves presented distinct correlation matrices for morphological and anatomical attributes, suggesting different response strategies to light intensity. The morphoanatomical results showed the capacity of A. verticillatus, E. pulchrum and U. verrucosum to respond significantly to light variations, through different structural modifications, which hinder the loss of water to the environment and maintain photosynthetic dynamics. Histochemical tests revealed the presence of special metabolites of the classes of terpenes and phenolic substances, in the entire leaf blade, in species from the three families