Plastids features and transfer cells occurrence in the phloem of portulaca mucronata and P. Hirsutissima (Portulacaceae)

Abstract

The species of the Portulacaceae of the Sena do Cipó, State of Minas Gerais, Brasil, were studied. In Po- rlutaca mucronata and P. hirsutissima transfer cells are companion and phloem parenchyma cells; they have the same secondary cell wall features, that is, short papillate protuberances which are uniformly distributed around the primary cell wall. These features arc similar in both species but they are very distinct from others referred in ihc literature: this could be useful in Taxonomy. The phloem plastids have a globular protein crystalloid, surrounded by proteinaceous filaments. In P. hirsutissima few starch grains may also be present, and this occurrence is considered primitive in the phylogenetic scale. These features agree with pre-sumptive evolution of those of leaf structure: P. hirsutissima has C3 photosynthesis structure, and P. mucronata C4 or Kranz anatomy.