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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