Chloroplast ontogenesis in Lippia citriodora L

Abstract

In the last decade it has been reported more and more frequently the pre sence of particular, electron-dense, membrane-bound plastid inclusions which, mostly, have been related to the building up of thylakoid membranes. Recently, in some plants with such plastid inclusions, it has been possible to evidence particular patterns of chloroplast ontogenesis and we think that many plants do not possess the chloroplast ontogenesis in conformity with the classic ontogenetic model. In Lippia aitriodora L. we could evidence one of this cases following its chloroplast ontogenesis from the shoot apex to adult leaves. (The leaf tissues have been sampled in the basal zone of successively older leaves. All the samples have been fixed with glutaraldehyde and osmium tetroxide and stained with uranyl acetate and lead citrate). The proplastids of shoot apex meristems show both membrane profiles filled with electron-dense material and membrane profiles with electron-transparent contents (fig. 1); sometimes the latter outlines are seen in continuity with the inner membrane of the plastid envelope.