Morfologia das plântulas, anatomia e venac¸ão dos cotilédones e eofilos de três espécies de Mimosa (Fabaceae, Mimosoideae)

Abstract

The post-seminal phase is the most critical on life cycle of plants, responsible for establishing a new individual. Mimosa is a large genus comprising species used for recovery of degraded areas; the knowledge of their juvenile stages is essential for their identification. This article describes and compares the seedling morphology, anatomy and venation of the cotyledons and eophylls of Mimosa daleoides, M. dolens var. anisitsii and M. orthacantha, adopting usual methods in morphology and light microscopy. The germination occurs between one and three days. Seedlings are phanero-epigeal-foliaceous, with expansion of cotyledons between two to five days after germination; cotyledons are similar, actinodromous and amphistomatic. The phyllotaxy of the cotyledons is opposite and of the eophylls is alternate. The number of leaflet pairs in the first eophyll ranges from two to three in M. dolens and M. daleoides var. anisitsii and from five to seven in M. orthacantha. The leaflet blade is anatomically similar between the species: amphistomatic, dorsiventral, with a well-developed layer of palisade parenchyma. Phenolic idioblasts are present throughout the epidermis of M. dolens var. anisitsii, which also displays lignified appendices in the leaflet edge. The venation pattern is brochidodromous, with some variations in M. orthacantha. The results allow the identification of Mimosa species in their juvenile stage, providing data that can support taxonomic and ecological studies of the genus.