Ipomoea asarifolia (Desr.) Roem. & Schult., Convolvulaceae, is a weed that infests agricultural areas and is toxic to cattle. In spite of its toxicity, the leaves of this plant are used in traditional remedies in the state of Bahia, Brazil. The present work describes the leaf anatomy of I. asarifolia and characterizes the exudates of its secretory structures. The leaves have a unistratifi ed epidermis composed of ordinary cells with straight to slightly sinuous anticlinal walls and thin cuticles. Paracytic stomata are found on both surfaces of the leaves at the same level as the ordinary epidermal cells. Trichomes producing polysaccharide secretions occur on the petiole and leaf blade and are considered colleters. The mesophyll is dorsiventral and the vascular bundle of the central vein is bicollateral. Two opposed nectaries occur on the petiole near the leaf blade. Each nectary is composed of a small canal with internal ramifi cations and numerous secretory trichomes. The laticiferous glands are articulated, not anastomosed, and are composed of large diameter cells with thin cell walls. The secretions of the laticiferous glands are lipidic.

RESUMO:A família Apocynaceae é caracterizada por possuir grande diversidade de estruturas secretoras como idioblastos, coléteres, laticíferos e nectários florais. Este estudo teve por objetivo caracterizar anatomicamente as estruturas secretoras nos órgãos vegetativos e reprodutivos de Secondatia densiflora e identificar as principais classes de compostos químicos nos idioblastos e na secreção dos coléteres vegetativos. Os idioblastos estão distribuídos por todos os órgãos aéreos da planta possuindo conteúdo na maioria das vezes denso e fortemente corado pela safranina. Alguns idioblastos apresentam secreção de aspecto granulado. Os testes histoquímicos evidenciaram apenas compostos fenólicos. Os laticíferos são do tipo anastomosado podendo ser observados em todos os órgãos estudados e identificados pelo conteúdo diferenciado e, em alguns casos, pela presença de paredes celulares mais espessas que as paredes das células parenquimáticas. O látex tem cor branca e aspecto leitoso, sendo extravasado logo que a planta é lesionada. Os coléteres vegetativos são do tipo padrão, formados por uma porção alongada que se afina em direção à extremidade. A epiderme secretora em paliçada delimita uma região parenquimática e o curto pedúnculo é coberto por epiderme não secretora de formato retangular. Todo coléter é recoberto por cutícula fina. A mucilagem é constatada tanto no interior das células secretoras quanto no meio extracelular pelo vermelho de rutênio e pela reação PAS. Os nectários florais têm origem receptacular, possuem uma epiderme que reveste toda estrutura, parênquima nectarífero, e feixes vasculares; são fundidos na base e livres na região apical constituindo cinco unidades distintas.Palavras-chave: idioblasto, coléter, laticífero, nectário floral ABSTRACT: Secretory structures in vegetative and floral organs of Secondatia densiflora A.DC. (Apocynaceae -Apocynoideae -Odontadenieae). The family Apocynaceae is characterized for showing a wide variety of secretory structures such as idioblasts, colleters, laticiferous glands and floral nectaries. The present study aimed to anatomically characterize the secretory structures in vegetative and reproductive organs of Secondatia densiflora and to identify the major classes of chemical compounds in idioblasts and in the secretion of vegetative colleters. Idioblasts are distributed all over the aerial organs of the plant and their content is usually dense and strongly stained with safranin. Some idioblasts have secretion of granulated aspect. Histochemical tests evidenced phenolic compounds only. Laticiferous glands are of the anastomosed type and can be seen in all the studied organs and identified by their distinct content and, in some cases, by the presence of cell walls that are thicker than those of parenchyma cells. Latex is white, milky and leaks as the plant is injured. Vegetative colleters are of the standard type and formed of an elongated portion that becomes thinner towards the end. The secretory palisade epidermis delimits a parenchymatic region, while the s...

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The genus Leiothrix (Eriocaulaceae) is restricted to South America, where most species occur in the Espinhaço mountain chain in Brazil. Seed ornamentation has a distinctive origin in the family and in most species of Leiothrix the seed coat has a striated pattern. The objective of this study was to evaluate the morphological aspects of seeds of Leiothrix as well as the post‐seminal development. Leiothrix seeds are elliptical or oval, the seed coat has a primary sculpture of isodiametric or hexagonal cells with concave periclinal walls and straight or sinuose anticlinal walls. Most species also have a secondary sculpture, which forms the striate ornamentation and this may be continuous or discontinuous with isolated, connected or cruciform annular striae. A comparative table of seed characters shows that most of them corroborate the current circumscription of the subgenera of Leiothrix. The seed coat striae expand with wetting and may help in seed imbibition during germination. Leiothrix seeds show a high germination rate and the post‐seminal development pattern is similar to that described for other species of Eriocaulaceae.

Leiothrix differs from other genera of Eriocaulaceae by having pistillate flowers with nectariferous and stigmatic branches that diverge at different heights on the style and staminate flowers with free or fused petals. To understand the ontogenetic processes that result in these morphological variations, we studied the development and floral vasculature in six species of the genus. In pistillate flowers, the nectariferous branches, which are in a carinal position, correspond to the apex of the carpels, whereas the stigmatic branches, in a commissural position, are formed by the marginal tissues of the carpels and initiate later than the nectariferous branches. The upper margins of the carpels elongate, forming a tubular structure that raises the stigmatic branches; the greater its development, the greater the distance between the stigmatic and nectariferous branches. In staminate flowers, the fusion of the petals appears to be post-genital in the median and apical portions and congenital in the more basal portion. Despite the differences in floral development, Leiothrix shares the same pattern of floral vasculature with other genera of Eriocaulaceae, exhibiting a central vascular plexus in the receptacle from which a single trace diverges for each sepal, petal and stamen. The staminodes are not vascularized. The dorsal carpellary bundles supply the nectariferous branches, but the ventral carpel bundles are reduced and are not involved in the supply of the ovules and stigmas. The differences in the height of insertion of the nectariferous branches are probably the result of selective pressure exerted by different groups of pollinating insects. Our hypothesis is that species in which the nectariferous branches are inserted below the stigmatic branches, and are therefore less accessible, exhibit a more specialized pollination system. The absence of nectariferous branches in L. angustifolia indicates secondary loss probably associated with spontaneous geitonogamy.