Chloroplast ontogenesis in <i>Lippia citriodora</i> L

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.</jats:p

Variations of the peach fruit transcriptome during ripening and in response to hormone treatments

Peach has fleshy climacteric fruits. Their ripening is controlled by both endogenous and exogenous signals to link the genetic determinants with the environmental conditions. Genomic tools, such as microarray RNA profiling, offer new prospects to study in a holistic way complex biological problems such as fruit ripening. We have adopted a microarray approach to monitor transcriptome changes in peach fruits during their transition from a pre-climacteric to a climacteric stage. Furthermore, the variations of gene transcription mediated by applications of exogenous ethylene and auxin to pre-climacteric fruits have also been analysed. In peach fruits the ripening process needs vast transcriptional changes to occur, and the hormone ethylene controls many of these changes. Among the many variations occurring during ripening, we observed that some genes coding for various isoforms of the glycolytic enzymes were up-regulated. Several hypotheses are presented to account for these results