Floral ultrastructure of two Brazilian aquatic-epiphytic bladderworts: Utricularia cornigera Studnicka and U. nelumbifolia Gardner (Lentibulariaceae).

Utricularia cornigera and Utricularia nelumbifolia are giant, aquatic-epiphytic species of carnivorous bladderwort from southeastern Brazil that grow in the central 'urns' of bromeliads. Both species have large, colourful flowers. The main aim of our study is to ascertain whether the prominent floral palate of U. cornigera and U. nelumbifolia functions as an unguentarius-i.e. an organ that bears osmophores. Floral tissues of both species were investigated using light microscopy, scanning electron microscopy, transmission electron microscopy and histochemistry. Floral palates of U. cornigera and U. nelumbifolia provide clear visual signals for pollinating insects. In both species, the palate possesses diverse micro-morphology, comprising unicellular, conical to villiform papillae and multicellular, uniseriate, glandular trichomes that frequently display terminal branching. The most characteristic ultrastructural feature of these papillae was the presence of relatively large, polymorphic plastids (chromoplasts) containing many plastoglobuli. Similar plastids are known to occur in the fragrance-producing (osmophores) and oil-producing (elaiophores) tissues of several orchid species. Thus, these palate papillae may play a key role in providing the olfactory stimulus for the attraction of insect pollinators. Nectariferous trichomes were observed in the floral spurs of both species, and in U. nelumbifolia, free nectar was also recorded. The location, micro-morphology, anatomy and ultrastructure of the floral palate of the two species investigated may thus indicate that the palate functions as an unguentarius. Furthermore, the flowers of these taxa, like those of U. reniformis, have features consistent with bee pollination.

Phylogenetic relationships of Xylella fastidiosa strains based on 16S-23S rDNA sequences.

In spite of the lack of resolution of Xylella fastidiosa phylogenetic relationships, parsimony analysis of the 16S-23S rDNA sequence from a wide range of hosts has been evaluated in this research. In order to establish an easier method for sequencing the spacer region completely, a new primer pair was designed. The sequences obtained revealed a higher level of variation than that found in 16S gene sequences, with similarity values ranging from 0.80 to 1.00. The cladogram constructed allowed the clustering of two major clades. From these results it has been possible to recognize the monophyletic grouping of some strains belonging to the same host, possibly representing only one infection process. However, for other hosts there is paraphyletic and polyphyletic grouping. This methodology followed from promising results regarding strain-host clustering. With the parsimony approach, hypothetical genealogical relationship among Xylella strains may be inferred.