Morphological and anatomical aspects of the leaves of Rhizophora mangle L. (Rhizophoraceae) under different lighting conditions

Resumen

The basic difference between sun and shade leaves arises because of the difference in their exposure to light intensities. To determine the adaptability of Rhizophora mangle L. leaves to different light conditions, we collected leaves from the upper peripheral region (sun leaves) and the internal lower part thereof (shade leaves) of six individuals. The following variables were analyzed: leaf thickness, palisade parenchyma, adaxial and abaxial epidermis, adaxial and abaxial cuticle, density, and stomatal index. The measurements were performed using microscopes equipped with an ocular micrometer. The sun leaves were found to be smaller, with more xeromorphic features such as thicker cuticle and adaxial and abaxial epidermis. The palisade parenchyma and mesophyll of the leaf blade in the sun leaves were found to be thicker than those in the shade leaves, although there was no significant difference in the cuticles of the abaxial face between both the leaf types. The frequency of stomata per square millimeter (average, 70/mm2) was also higher in the sun leaves than in the shade leaves (47 showed/mm2), and there were no differences in the width and length between them to the two types of leaves. Variations between sun and shade leaves indicated an adaptive ability of R. mangle to remain active under varying lighting conditions.