Developmental and Structural Section
Cotta Coutinho , Italo Antonio , Akemi Ponce Otuki, Sara , Ferreira Fernandes, Valéria , STROZI ALVES MEIRA , RENATA MARIA .
Diversity of secretory structures in Urena lobata L.: ontogenesis, anatomy and biology of the secretion.
Urena lobata L. is weedy pantropical Malvaceae species commonly found in Brazil. Despite being an important plant species used in folk medicine, we found no records of anatomical or histochemical study regarding this species. Besides, even though secretory structures have been largely reported for many Malvaceae species, the only secretory structures reported for U. lobata are the 1- rarely 3 glands placed along the palmate-veined leaves. This study aims to describe the development and characterize the secretory structures present on both leaves and flowers of U. lobata. Ordinary light microscopy techniques and scanning electron microscopy for the structural characterization were carried on. Histochemical tests followed by control sections were performed simultaneously as required for each test. The following secretory structures were observed: leaf-tooth hydathodes, secretory trichomes, both extrafloral and floral nectaries and mucilage idioblasts. Hydathodes show water pores placed at the same level of the epidermis and are vascularized exclusively by xylem. Tracheids vein endings abut the epithem which is delimited by a single or bi-layered sheath containing phenolic compounds. Clavate secretory trichomes were observed spread all over the leaf blade, outside the ovary and at the upper adaxial side of the sepals. The abaxial leaf glands are vascularized by both phloem and xylem and are made up by 3-6 layers of secretory parenchyma and several cylindrical multicellular secretory trichomes on de epidermis. Histochemical analyses proved that such glandular trichomes are nectariferous trichomes that secrete glucose, polysaccharides, pectins, mucilage, proteins and lipids. Similar structural floral nectaries were observed on the base of the adaxial side of the sepal. Lipids were not observed in the secretion of the floral nectaries, only polysaccharides, pectins, mucilage and proteins. Idioblasts were observed in the leaf blade, petiole, and stem as well as in all flower parts but petals. During the idioblasts ontogenesis, the idioblast precursor cells are arranged in a longitudinal series. As the idioblasts development goes on, such series of cells have their transverse cell walls dissolved in a way that a long tube is formed, similarly to what happens to anastomosed laticifers. Polysaccharides, pectins, mucilage and proteins were the components found in the idioblast secretion. The characterization of the secretory structures is important for further ecological studies involving plant/animal interactions as well as studies with taxonomical approaches. The authors wish to thank CPNq, CAPES, FAPEMIG and Floresta Escola for research grants and/or financial support.
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1 - Universidade Federal De Vicosa, Departamento De Biologia Vegetal, Av.: PH Rolfs S/n - Campus Universitario, Vicosa - MG, N/A, 36570900, Brazil
2 - Universidade Federal de Vicosa
3 - UNIVERSIDADE FEDERAL DE VIÇOSA, Av. P. H. Rolfs, S/n, Centro, Campus UFV, Viçosa/Minas Gerais, N/A, 36570-000, Brazil
Presentation Type: Oral Paper:Papers for Sections
Location: Pines North/Boise Centre
Date: Tuesday, July 29th, 2014
Time: 2:15 PM
Candidate for Awards:Katherine Esau Award