Development of carpels and ovules in Dialypetalanthus fuscescens Kuhlm. (Rubiaceae): an enigmatic taxon

ABSTRACT Dialypetalanthus is a monospecific genus that occurs in the Amazon Basin of Brazil, Bolivia and Peru and occupies a controversial position among the Rubiaceae. We continue this taxonomic discussion with the overall aim of clarifying the systematic position of D. fuscescens within the Rubiaceae. To accomplish this, we analyzed the ontogeny of its gynoecium, in particular the floral meristem, as well as the development of the carpels and cauline placentation. Gynosporogenesis and the differentiation of the carpellary septa and ovules were also described. Dialypetalanthus fuscescens was classified according to evolutionary diagrams found in the literature. The following characteristics were observed in D. fuscescens: 1) permanence of the floral meristem in the central basal part of the early flower bud; 2) dual origin of carpellary septum; 3) trizonate ovular primordia with only one fertile gynospore per ovule; and 4) cellular proliferation in the chalazal region. Embryological results confirm the classification of D. fuscescens in the subfamily Ixoroideae. These results are distinct from any others previously proposed in the evolutionary diagram. Therefore, we conclude that this study has presented evidence strongly suggesting that Dialypetalanthus possesses new morphological-type of ovule we refer to as the Dialypetalanthus-type

A regioselective coating onto microarray channels of bamboo with chitosan-based silver nanoparticles

In this investigation, bamboo (Dendrocalamus giganteus Munro) timbers were coated selectively into vascular vessel bundles with a potential antimicrobial colloidal solution of silver nanoparticles (Ag-NPs). Electric charge and size of Ag-NPs, with different charged organic ligands (trisodium citrate and chitosan), affect their self-sorting in different anatomical structures of bamboo when submitted up to 20 impregnation cycles through a vacuum system. Physicochemical characterization of Ag-NPs was performed by spectroscopic techniques and electron microscopy. Confocal laser scanning microscopy and scanning electron microscopy were employed to characterize natural bamboo. Qualitative and quantitative determination of the metal coating in bamboo specimens was performed with X-ray microtomography (μCT), energy-dispersive X-ray spectroscopy, and X-ray diffraction. μCT revealed a gradient deposition of citrate-capped Ag-NPs into the parenchyma tissue with the higher concentration at the outer part of the bamboo. On the other hand, the chitosan-capped Ag-NPs were deposited mainly in the vessel bundles