Structural aspects of cypsela and seed development of Trichocline catharinensis (Cabrera): a Brazilian endemic species.

This is the first study to describe in a timescale morphohistological and ultrastructural characteristics of fruit (cypsela) and seed development in Trichocline catharinensis, which was completed 21 days after anthesis (DAA). At anthesis, we identified an ovary with three differentiated regions, including the inner epidermis, inner part, and outer epidermis. The mature ovule showed an integument with the outer epidermis, integumentary parenchyma, and endothelium. Cells around the endothelium form the periendothelial zone with thick cell walls that showed Periodic acid-Schiff (PAS)-positive reaction. The periendothelial zone and endothelium showed degradation of the cells during embryogenesis. The main stages of embryo development from fecundation through mature seed were identified. The ripe cypsela showed the pericarp (exocarp), seed coat (exotesta), and remaining endosperm surrounding the embryo. Mature embryos were straight with shoot apical meristem (SAM), and root apical meristem (RAM) was separated by the hypocotyl. Light microscopy (LM) and transmission electron microscopy (TEM) analyses indicate cells with characteristics of meristem cells, as well as proteins and lipid bodies and mitochondria with few cristae in cotyledon cells. Our findings provide insight into taxonomic and physiological studies by detailing cypsela and seed ontogenesis from an endemic and vulnerable Asteraceae from southern Brazil. This study is also a starting point for establishing the biological criteria for seed harvesting and future studies of seed physiology and conservation of plant genetic resource.

Reproductive Biology of Varronia curassavica Jacq. (Boraginaceae)

ABSTRACT Varronia curassavica, a subshrubby medicinal species associated with restinga in the Atlantic Forest, has been exploited by local people and the pharmaceutical industry. Indeed, restingas have experienced a continuous process of degradation, and thus, with species and ecosystem both at risk, efforts to support conservation actions are required. The present study aimed to evaluate aspects of V. curassavica reproductive biology. To accomplish this, morphological characterization was performed by monitoring flowering events. The availability of nectar and pollen, as well as the frequency and behavior of floral visitors and dispersers, was also evaluated. This species exhibits both heterostyly and protogyny. Anthesis is diurnal, and flowers last less than a day. The high number of flower and fruit abortions suggests that mechanisms, such as self-incompatibility intra-morphs and easily detached flowers, contribute to reduced fruit production. The high diversity of floral visitors indicate a generalist pollination syndrome. Diptera, Hymenoptera and Lepidoptera were the main pollinators, and nectar was the main resource sought by these insects. Fruits were dispersed by birds and ants. It can be concluded that the interaction of V. curassavica with several species is a key factor in its own survival and for maintaining the biological diversity of restinga.

Reproductive Biology of Varronia curassavica Jacq. (Boraginaceae).

Varronia curassavica, a subshrubby medicinal species associated with restinga in the Atlantic Forest, has been exploited by local people and the pharmaceutical industry. Indeed, restingas have experienced a continuous process of degradation, and thus, with species and ecosystem both at risk, efforts to support conservation actions are required. The present study aimed to evaluate aspects of V. curassavica reproductive biology. To accomplish this, morphological characterization was performed by monitoring flowering events. The availability of nectar and pollen, as well as the frequency and behavior of floral visitors and dispersers, was also evaluated. This species exhibits both heterostyly and protogyny. Anthesis is diurnal, and flowers last less than a day. The high number of flower and fruit abortions suggests that mechanisms, such as self-incompatibility intra-morphs and easily detached flowers, contribute to reduced fruit production. The high diversity of floral visitors indicate a generalist pollination syndrome. Diptera, Hymenoptera and Lepidoptera were the main pollinators, and nectar was the main resource sought by these insects. Fruits were dispersed by birds and ants. It can be concluded that the interaction of V. curassavica with several species is a key factor in its own survival and for maintaining the biological diversity of restinga.

Reproductive Strategy of the Polyploid Species Varronia curassavica Jacq. in Restinga Environment.

This study aimed to elucidate the breeding strategies of Varronia curassavica, an important medicinal species associated with Brazilian restinga. This was accomplished by combining phenological and genetic data. Every 2 weeks over a period of 2 years, we measured flowering and fruiting phenology to evaluate the activity and intensity of phenophases (n = 60). We evaluated the mating system, pollen ovule ratio and genotypes from progeny and mother plants using 8 nuclear microsatellite loci. We observed flowering and fruiting of V. curassavica at low intensity throughout the entire year, but with 2 distinct peaks, one of which was seasonal, corresponding to the period of gradual increase of temperature and photoperiod. Overlapping of flowering and fruiting strategies favors gene flow among different groups of individuals and between populations by attraction of fauna throughout the year. Analysis of the mating system indicates that V. curassavica is a typical outcrossed species (t^ = 0.98; pollen/ovule ratio = 7087.50). Combining phenology with genetic studies improved our understanding of the reproductive strategies of this species. The typical outcrossing system of V. curassavica reflects the existence of functional self-incompatibility mechanisms still unaffected by changes in genetic balance by polyploidy.

Morpho-histodifferentiation of Billbergia Thunb. (Bromeliaceae) nodular cultures.

Nodule cultures are formed through an intermediate morphogenetic route that lies between organogenesis and somatic embryogenesis. Although well described in many species, different aspects of the morphological and histological development of nodules remain to be clarified. Based on their threatened status and high ornamental value, Billbergia alfonsi-joannis and Billbergia zebrina, two epiphytic bromeliad species endemic to the South American Atlantic Forest, were studied. Nodular cultures were induced to grow from nodal segments taken from etiolated seedlings grown in vitro for 12 weeks in the dark on MS medium supplemented with 1 µM TDZ. Samples were taken for analysis weekly over 8 weeks of growth and analyzed under light, transmission electron, and scanning electron microscopes. Morphological and histological analysis showed that nodular clusters originated from stem pericycles and consisted of a polycenter, cambial tissue, cortical parenchyma, and a covering tissue. The polycenter consisted of an organizational center dispersed in parenchymal tissue. Each organizational center was formed by a vascular system surrounded by a bundle sheath. A cambial tissue surrounded these polycenters, promoting the regeneration of new nodules and leading to the formation of buds and roots. Primary nodules could generate secondary nodules in a repetitive process. Thus, histological analysis revealed the origin and formation of nodular cultures. These new data will support the establishment of micropropagation protocols and regeneration on a large scale for these species.