Leaf epidermal micromorphology of the abaxial surface of Myrcia DC. species (Myrtaceae)

Myrtaceae is widely distributed in tropical regions, playing significant ecological and economic roles. Within this family, Myrcia stands out for its taxonomic complexity due to high morphological homogeneity, which complicates the identification of species and sections. This study aims to analyze and describe micromorphological characteristics of Myrcia leaves to contribute to the characterization of the genus and its infrageneric groups, as well as to generate data to support future taxonomic studies. The abaxial surface of leaves from 73 Myrcia species was analyzed using scanning electron microscopy (SEM). Characteristics of stomata, cuticle, epicuticular waxes, and trichomes were observed. Stomata, classified as anomocytic and paracytic, showed variations in height relative to epidermal cells. The cuticle exhibited smooth and striated patterns, while epicuticular waxes ranged from smooth to plate-like, fimbriate, and granular. Glandular and non-glandular trichomes, the latter with uniseriate, dibrachiate, stellate, and branched forms, were documented, revealing wide variation in density, distribution and length. None of the analyzed characters distinctly defined the ten infrageneric groups of Myrcia due to high plasticity. However, some patterns were observed, such as the predominance of dibrachiate trichomes in M. sects. Calyptranthes and Sympodiomyrcia. This study provides valuable new data for the taxonomy of Myrcia and future micromorphological research.