How can structure and nectar composition explain the secretory process in super productive nuptial nectaries of Mabea fistulifera Mart. (Euphorbiaceae)?

Mabea fistulifera, a species pollinated mainly by diurnal and nocturnal vertebrates, presents pendulous inflorescences with approximately 70 pairs of nuptial nectaries (NNs). These NNs exude voluminous nectar drops that defy gravity, remaining exposed at the inflorescence for more than a day. We aimed to investigate the NN secretory process and the unique nectar presentation of M. fistulifera. NNs and their exudate were collected at different secretory stages and submitted to structural studies and chemical analysis. The epidermis is devoid of stomata and constitutes the main site of synthesis for non-sugar metabolites found on nectar and nectar-coating film. Nectary parenchyma presents few small starch grains, and vascular strands are distributed until the nectary parenchyma cells close to the epidermis. Vascular tissues at the nectary parenchyma seem to provide sugar and water for the nectar. A film composed of lipids, alkaloids, and proteins covers the nectar drops. The film guarantees the nectar offering for several hours, as it minimizes water loss and prevents falls by gravitational action. The release of large nectar drops is intrinsically linked to the NN anatomical traits and the exudate composition. Low sugar concentration and predominance of hexoses in M. fistulifera nectar are essential for maintaining nectar exudation for many hours, which results in the visitation of a broad spectrum of pollinators.

Mutagenic activity and chemical composition of phenolic-rich extracts of leaves from two species of Ficus medicinal plants.

Plant species from the Ficus genus are widely used as food, and in folk medicine as anti-inflammatory, antioxidant and anticancer agents, although some of these species are known to produce adverse effects. The aim of this study was to determine and compare the chemical composition as well as in vitro antioxidant and mutagenic activity of the aqueous extracts of leaves from F. adhatodifolia and F. obtusiuscula. Phytochemical screening using thin-layer chromatography identified 6 classes of secondary metabolites in the extracts. Total phenolic content was estimated by the Folin-Ciocalteau method and the phenolic profile was determined by UPLC-DAD-ESI/MS/MS. Antioxidant activities were evaluated by the DPPH radical assay and by the ß-carotene/linoleic acid system. Mutagenic activity was measured by the Salmonella typhimurium reverse mutation test with 4 strains, in both the presence and absence of metabolic activation. Flavonoids, coumarins, and tannins were detected in both extracts, and 6 major derivatives were identified as flavone compounds. Antioxidant activities were demonstrated for both extracts, while F. obtusiuscula contained higher concentrations of phenolic compounds. Mutagenic activity of the TA97 strain without metabolic activation was observed for both tested extracts, as well as the TA102 strain with metabolic activation. In addition, the extract of F. adhatodifolia was shown to be mutagenic to the TA102 strain without metabolic activation. Evidence indicates that the use of teas obtained from these two plant extracts in folk medicine may raise concerns and needs further investigation as a result of potential pro-oxidant mutagenic effects in the absence or presence of metabolic activation.

Timing of pollen release and stigma receptivity period of Piper vicosanum: New insights into sexual reproduction of the genus.

PREMISE OF THE STUDY: Dichogamy is a common characteristic among angiosperms, including Piper species. In this genus, the tiny flowers are morphologically similar and have an asynchronous stamen development. However, there is no information on the duration of stigma receptivity and whether it overlaps with pollen release. To better understand mechanisms of floral function in Piper vicosanum, we provide a detailed characterization of the timing of pollen release from the four stamens and the period of stigma receptivity and exposure mode of the receptive areas. METHODS: We investigated plants of a natural population in a semideciduous seasonal forest (Viçosa, Minas Gerais State, southeastern Brazil), based on chemical tests, light microscopy, and scanning electron microscopy analyses. KEY RESULTS: Incomplete protogyny-a mechanism that favors outcrossing-was recorded. The period of stigma receptivity was long (14 d), and the sequential exposure and senescence of stigmatic papillae occurred gradually and in a basipetal direction. Pollen release began 2-6 d after the beginning of the pistillate phase, with an average pollen viability of 87.7%, during the bisexual flower phase. Pollen was released for up to 6 d and occurred in one stamen at a time. The fruit set observed in tests of self-pollination indicated self-compatibility. CONCLUSIONS: The gradual and sequential exposure of stigmatic papillae in P. vicosanum flowers is described here as the mechanism for the long duration of receptivity. Anther development and pollen release were also sequential. These findings are yet unreported reproductive characteristics of the genus and offer new perspectives for future studies on the floral biology of other Piper species.

Leaf anatomy and histochemistry of three species of Ficus sect. Americanae supported by light and electron microscopy.

In this work the leaf anatomy of three species of Ficus section Americanae (Miq.) Miq. from Brazil, whose leaves and latex are used in folk medicine is reported. The work was carried out using light and scanning electron microscopy in order to characterize these species and to evaluate their taxonomic significance, and also contribute to the quality control of their ethnodrugs. The three species (Ficus cyclophylla, Ficus elliotiana, and Ficus caatingae) showed hypostomatic leaves, anomocytic stomata, straight epidermal cell outlines, and a dorsiventral mesophyll. Some micro-morphological characters such as density and distribution of epicuticular waxes, glandular trichomes, the length and width of stomata, as well as the palisade of mesophyll and petiole outlines proved to be the most useful and distinctive characters for the separation of species. These may contribute as additional support for the taxonomy of the section and for the quality control of their ethnodrugs.

Anatomy, histochemistry and micromorphology of leaves of Solanum granuloso-leprosum dunal / Anatomia, histoquímica e micromorfologia de folhas de Solanum granuloso-leprosum dunal

In the present work the anatomical, histochemical and micromorphological features of S. granuloso-leprosum leaves were approached in order to evaluate its characteristics associated with its pioneer role. Glandular and non-glandular trichomes were observed on both epidermal surfaces, although in greater number on the ab axial surface. Stellate trichomes presented a thick lignified cell wall. Leaves were amphiestomatic with a single palisade layer and a slightly smaller spongy parenchyma. The epidermal cells of the abaxial surface were shorter than the adaxial ones, both with stomata paracytic. Vascular bundles were bicolateral and idioblasts with conspicuous crystalliferous inclusions were observed in the mesophyll. Lipid drops were evidenced in the spongy parenchyma by Sudan III, Nile Blue, Nadi reagent and Sudan Black histochemical tests. Negative results for alkaloids and phenol compounds were observed. The evaluated anatomical and hystochemical data highlights mesophytic characteristics in accordance with S. granuloso-leprosum pioneer plant role.

No presente trabalho foi abordada a anatomia, histoquímica e micromorfologia de folhas de S. granuloso-leprosum no intuito de se levantar características associadas a sua função de espécie pioneira. Tricomas glandulares e não glandulares foram observados em ambas as faces da epiderme, apesar de maior número na superfície abaxial. Tricomas estrelados apresentaram uma parede espessa e lignificada. As folhas são anfiestomáticas com uma única camada de paliçada e um parênquima lacunoso com células menores que as do paliçádico. As células da face abaxial da epiderme são menores, e ambas as faces apresentam estômatos paracíticos. Os feixes vasculares são bicolaterais e idioblastos com inclusões cristalinas conspícuas. Gotas de lipídeo foram evidenciadas no parênquima lacunoso com os testes histoquímicos de Sudan III, azul do Nilo, reagente de Nadi e Sudan Black. Foram observados resultados negativos para alcaloides e fenóis. Os dados anatômicos e histoquímicos avaliados permitiram verificar que S. granuloso-leprosum apresentam características mesófilas, os quais estão em conformidade com o seu papel fitossociológicos como pioneira.

A NOVEL EPIPHYTIC CYANOBACTERIAL SPECIES FROM THE GENUS BRASILONEMA CAUSING DAMAGE TO EUCALYPTUS LEAVES(1).

A cyanobacterial mat colonizing the leaves of Eucalyptus grandis was determined to be responsible for serious damage affecting the growth and development of whole plants under the clonal hybrid nursery conditions. The dominant cyanobacterial species was isolated in BG-11 medium lacking a source of combined nitrogen and identified by cell morphology characters and molecular phylogenetic analysis (16S rRNA gene and cpcBA-IGS sequences). The isolated strain represents a novel species of the genus Brasilonema and is designated Brasilonema octagenarum strain UFV-E1. Thin sections of E. grandis leaves analyzed by light and electron microscopy showed that the B. octagenarum UFV-E1 filaments penetrate into the leaf mesophyll. The depth of infection and the mechanism by which the cyanobacterium invades leaf tissue were not determined. A major consequence of colonization by this cyanobacterium is a reduction in photosynthesis in the host since the cyanobacterial mats decrease the amount of light incident on leaf surfaces. Moreover, the cyanobacteria also interfere with stomatal gas exchange, decreasing CO2 assimilation. To our knowledge, this is the first report of an epiphytic cyanobacterial species causing damage to E. grandis leaves.