Morfo-anatomia comparada das folhas do par vicariante Plathymenia foliolosa Benth. e Plathymenia reticulata Benth. (Leguminosae - Mimosoideae)

Abstract

(Comparative morpho-anatomy of leaves from the vicariant pair Plathymenia foliolosa Benth. and Plathymenia reticulata Benth. (Leguminosae-Mimosoideae)). The bipinnate adult leaves of P. foliolosa from the forest (Minas Gerais) and P. reticulata from the cerrado vegetation of Brasilia (DF), Brazil, were studied. All parts of the leaves were examined under the light microscope with normal and polarized light. P. reticulata leaflets are larger than those of P. foliolosa. The anatomical structure in all parts shows subtle differences which may be of ecological importance. The stomata occur either at the same level as the adjacent epidermal cells or they may be slightly sunken in P. reticulata or slightly raised in P.foliolosa. The leaflet blade is wider in P. reticulata and the mesophyll cells are more tightly arranged. The leaflet blade is hypostomatic, dorsiventral with two layers of palisade parenchyma in P. reticulata and one layer in P. foliolosa. The cutinization process is more intense in the epidermal cell walls of P. reticulata. Calcium oxalate crystals are more abundant in P. foliolosa although crystal redissolution was seen in both species. Stronger scleromorphism (from the anatomical point of view), greater amount of phenolic deposits and gelatinous fibers are features more conspicuous in P. reticulata. The similar structural organization recorded for the two vicariant species agrees with their close taxonomic relationship and the differential anatomical features may be related to the environmental factors of the species' habitat.