MORFOANATOMIA DAS MARGENS FOLIARES EM ESPÉCIES DE CELASTRACEAE NEOTROPICAIS: UMA ASSOCIAÇÃO COM GLÂNDULAS?

Abstract

Celastraceae, a family within the order Celastrales, presents a complex taxonomy, with recent reclassifications currently recognizing 13 subfamilies. The family exhibits a wide variety of leaf margin types, including entire, crenate, serrate, spiny, dentate, spiny-dentate, and glandular-dentate forms. This morphological trait, particularly the presence of glands, has been used by taxonomists to delimit taxa at various hierarchical levels. Colleters associated with leaf margins have so far been reported in only two species of the family. In this context, the present study aimed to investigate the presence of glands associated with different types of leaf margins in Neotropical species of Celastraceae, through morphoanatomical and micromorphological analyses, and to confirm the identity of these glands. A total of 21 species belonging to 12 genera and four Neotropical subfamilies of Celastraceae (Celastroideae, Salacioideae, Hippocrateoideae, and Maytenoideae) were sampled. Young and mature leaves were obtained from herbarium specimens and/or field collections in areas in the Cerrado and Atlantic Forest, and processed using standard techniques. Four types of leaf margins were observed: eight species with entire margins, ten with crenate, one with serrate, and three with spinescent margins. Leaf venation analysis revealed a predominance (71.43%) of the semicraspedodromous pattern, with marginal endings varying between looped, pointed, incomplete, or absent. Glands were found in 18 of the 21 species, being absent in those with spinescent margins (Monteverdia aquifolium and M. ilicifolia) and in Schaefferia argentinensis, which has an entire margin. These glands position, their secretory activity, anatomical structure, lack of vascularization, and secretion composition allowed their identification as colleters. These colleters are of the standard type, producing a polysaccharide-rich mucilaginous secretion. They are deciduous in mature leaves, leaving scars. The highest colleters density was observed in the subfamily Maytenoideae. The presence of colleters on the leaf margins of Neotropical species of Celastraceae proved to be a common feature, reinforcing the relevance of this secretory structure to the taxonomy of the family, as it may serve as a stable and distinctive morphological character useful for the delimitation of taxonomic groups.