Foliar secretory structures in Crotoneae (Euphorbiaceae): Diversity, anatomy, and evolutionary significance.

PREMISE OF THE STUDY: Phylogenetic and morphological studies have helped clarify the systematics of large and complex groups such as the tribe Crotoneae (Euphorbiaceae). However, very little is known about the diversity, structure, and function of anatomical features in this tribe. Crotoneae comprises the species-rich pantropical genus Croton and six small neotropical genera. Here we characterized the anatomy of leaf secretory structures in members of this tribe and explored their function and evolutionary significance. METHODS: Young and mature leaves of 26 species were studied using standard anatomical light microscopy techniques. Three sections of Croton and one representative of Brasiliocroton and Astraea were sampled. KEY RESULTS: We identified five types of secretory structures: laticifers, colleters, extrafloral nectaries, idioblasts, and secretory trichomes. Laticifers were present in all species studied except Croton alabamensis, which instead presented secretory parenchyma cells. Articulated laticifers are reported in Crotoneae for the first time. Colleters of the standard type were observed in the majority of the sampled taxa. Extrafloral nectaries were present in section Cleodora and in B. mamoninha, but absent in section Lamprocroton and Astraea lobata. Idioblasts were spread throughout the palisade and/or spongy parenchyma in most of the studied species. Secretory trichomes were restricted to Lamprocroton except for C. imbricatus. CONCLUSIONS: This study revealed a high diversity of secretory structures, including novel ones, in one of the largest clades of Euphorbiaceae. Our results are promising for investigations on the anatomical and ecophysiological bases of species diversification within Euphorbiaceae.

Methacrylate: An alternative fixing agent for identifying the botanical origin of propolis.

PREMISE: A new technique was developed to identify the botanical origin of propolis, a resin-like material made by bees by mixing saliva and beeswax with plant buds and exudates, using methacrylate for permanent slide preparation. METHODS AND RESULTS: Propolis samples were fixed in methacrylate to produce permanent slides. The anatomical structures of the plant fragments in the methacrylated propolis were compared with propolis slides prepared using conventional techniques that consist of propolis sediment obtained during a series of solvent reactions, filtration, and centrifugations, which cost a similar amount to produce. The techniques resulted in qualitative differences between the slides obtained. The methacrylated propolis sections allowed the detailed observation and identification of plant anatomical structures that were obscured in samples prepared using the conventional procedure. This clarity enabled the detailed evaluation of valuable taxon-diagnostic characters in a permanent slide, which can also be used for histochemical tests. CONCLUSIONS: The methacrylated embedding of propolis is an affordable technique that could be implemented as a routine laboratory procedure. This new technique enables the efficient determination of the botanical origin of propolis.

Anatomy of vegetative organs of Scutellaria agrestis, a medicinal plant cultivated by riverine populations of the Brazilian Amazon

Scutellaria agrestis A. St. -Hil. ex Benth. , Lamiaceae (trevo-roxo) is cultivated for medicinal purposes by residents of the riverine communities in the State of Amazonas, Brazil. This study aimed to characterize the anatomy and to make histochemical analysis on vegetative organs of S. agrestis. Samples of the leaf, stem and root were collected from five plants cultivated by the communities located in the Solimões river, Amazon. These samples were fixed and prepared following standard techniques for scanning electron microscopy and for light microscopy. Histochemical tests were carried out on sections to detect the main classes of compounds present in the secretion. Numerous glandular trichomes are seen in both leaf and stem of S. agrestis. The leaves are amphi-hypostomatics and show dorsiventral mesophyll. Hydathodes are present at the tip of the marginal teeth. Anthocyanin pigments occur into the epidermal cells of the stem, petiole, and abaxial leaf surface. The petiole is concave-convex shaped and bears collateral vascular bundles. The stem showed square-shaped, evident endoderm, collateral vascular bundles and parenchymatous pith. The root displays a typical protostelic structure. Idioblasts containing mucilage and phenolic compounds occur in the cortex. These data are important, as they can be useful to identify this species, contributing to the quality control of the medicinal plant.

Anatomical and histochemical characterization of extrafloral nectaries of Prockia crucis (Salicaceae).

Besides being vital tools in taxonomic evaluation, the anatomy of plant secretory structures and the chemical composition of their secretions may contribute to a more thorough understanding of the roles and functions of these secretory structures. Here we used standard techniques for plant anatomy and histochemistry to examine secretory structures on leaves at different stages of development of Prockia crucis, to evaluate the origin and development of the structures, and to identify the disaccharides and monosaccharides in the exudates. Fructose, glucose, and sucrose constituted up to 49.6% of the entire secretion. The glands were confirmed to be extrafloral nectaries (EFNs); this is the first report of their presence in the genus Prockia. These EFNs are globular, sessile glands, with a central concavity occurring on the basal and marginal regions of the leaf. The epidermis surrounding the concavity is secretory, forming a single-layered palisade that strongly reacts with periodic acid-Schiff's reagent (PAS) and xylidine Ponceau, indicators of total polysaccharides and total proteins, respectively, in the exudate. On the basis of the similarity of these glands to the salicoid teeth in Populus and Salix, we suggest that these three taxa are phylogenetically close.

Anatomy and histochemistry of the vegetative organs of Cissus verticillata: a native medicinal plant of the Brazilian Amazon

The purpose of this paper was to carry out an anatomical and histochemical analysis of the vegetative organs of Cissus verticillata (L.) Nicolson & C.E. Jarvis, Vitaceae, to contribute for the attest the taxonomic identity of the medicinal plant. Samples from root, stem, leaf and tendril were cleared, dissociated and processed according to the usual methodology for observation under light and scanning electron microscopes. Histochemical tests were performed in order to identify polysaccharides, phenolic and lipid compounds. The C. verticillata root is typically protostelic, and the stem is eustelic with collateral bundles. The tendril presents structural organization similar to the stem, suggesting a common origin for both. The petiole has an epidermis with ornamented cuticle; the cortex is composed of collenchyma and parenchyma, and the vascular tissues are arranged in collateral bundles. The leaf blade is amphistomatic with non-glandular and glandular trichomes, and the mesophyll is dorsiventral. The identification of the idioblasts as secretion site of the phenolic compounds, mucilage and terpenoids as being responsible for the potential activity of the plant is of fundamental importance for future bioprospecting research on this species.

Chemical composition and histochemistry of Sphagneticola trilobata essential oil

Anatomical and histochemical investigations of Sphagneticola trilobata (L.) Pruski, Asteraceae, secretory structures in leaves and stems and the seasonal variation of essential oils were carried out. Histochemical techniques enabled the specific location of the essential oil accumulation in the internal (canals) and external structures (trichomes). Histochemical analysis showed that the secretory trichomes produced steroids. The highest yield was obtained from plants collected in winter, when it was registered low temperature and precipitation. The essential oil was characterized by high percentage of hydrocarbon sesquiterpenes, hydrocarbon monoterpenes and low levels of oxygenated sesquiterpenes. The major components were germacrene D (11.9-35.8%), α-phellandrene (1.4-28.5%), α-pinene (7.3-23.8%), E-caryophyllene (4.6-19.0%), bicyclogermacrene (6.0-17.0%), limonene (1.8-15.1%) and α-humulene (4.0-11.6%). The percentage of most of the individual constituents present in S. trilobata essential oil changed significantly during the months.

Plant Origin of Green Propolis: Bee Behavior, Plant Anatomy and Chemistry.

Propolis, a honeybee product, has gained popularity as a food and alternative medicine. Its constituents have been shown to exert pharmacological effects, such as anti-microbial, anti-inflammatory and anticancer. Shoot apices of Baccharis dracunculifolia (alecrim plant, Asteraceae) have been pointed out as sources of resin for green propolis. The present work aimed (i) to observe the collecting behavior of bees, (ii) to test the efficacy of histological analysis in studies of propolis botanical origin and (iii) to compare the chemistries of alecrim apices, resin masses and green propolis. Bee behavior was observed, and resin and propolis were microscopically analyzed by inclusion in methacrylate. Ethanol extracts of shoot apices, resin and propolis were analyzed by gas chromatography/mass spectroscopy. Bees cut small fragments from alecrim apices, manipulate and place the resulting mass in the corbiculae. Fragments were detected in propolis and identified as alecrim vestiges by detection of alecrim structures. Prenylated and non-prenylated phenylpropanoids, terpenoids and compounds from other classes were identified. Compounds so far unreported for propolis were identified, including anthracene derivatives. Some compounds were found in propolis and resin mass, but not in shoot apices. Differences were detected between male and female apices and, among apices, resin and propolis. Alecrim apices are resin sources for green propolis. Chemical composition of alecrim apices seems to vary independently of season and phenology. Probably, green propolis composition is more complex and unpredictable than previously assumed.