Ontogenia e anatomia foliar de quatro espécies do gênero Bauhinia L. (Fabaceae, Cercidoideae)

Abstract

Bauhinia, a genus of Fabaceae, is well represented in Brazilian flora and has representatives with variable morphology, which results in controversy about leaf classification. Thus, to elucidate the question, the ontogeny of four species with different morphologies: Bauhinia bauhinioides and B. hagenbeckii (bifoliolate); B. pentandra and B. variegata (bilobed). Triplicates of shoot apical meristems with leaf primordia and mature leaves were collected and/or obtained from herbarium material for each of the evaluated species. Herbarium samples underwent a rehydration process and fixation, whereas fresh samples were directly fixed. The samples were embedded in historesin, sectioned, stained with 1% Toluidine Blue, and analyzed. The ontogeny is similar among the species that are fused during the primary morphogenesis and have the degree of fusion established at the end of the secondary morphogenesis.The mucro became distinct from the blade in primary morphogenesis and shows shape variations during secondary morphogenesis. The leaf morphology seems to be related with the decrease of the meristematic activity on the leaf blade close to the mucro. All primordia shows low quantities of idioblasts and high density of trichomes uniseriate and cavitated, whereas the opposite occurs on mature leaves. Variations were observed between the morphogenesis phases and the species primordia. Equally, variations on the arrangement of the vascular bundles are observed on petiolate and proximal pulvinus, but the vascular arrangement of all distal pulvinus have four bundles. Thus, all species studied have compound leaves and the different degrees of division in mature leaves are established at secondary morphogenesis.