Coléteres dendróides em Alibertia sessilis (Vell.) K. Schum., uma espécie não-nodulada de Rubiaceae

Abstract

-(Dendroid colleters of Alibertia sessilis (Vell.) K. Schum., a non-nodulated Rubiaceae species). This paper describes the distribution, structure and histochemistry of the colleters in vegetative and reproductive apices of Alibertia sessilis (Vell.) K. Schum., a native Rubiaceae species of the Brazilian "cerrado". In this family, dendroid colleters have been associated with the presence of bacterial nodules in the leaves. Samples were prepared according to common light and scanning electron microscopy techniques, and histochemical assays involved freshly collected material. Colleters are dendroid and occur on the adaxial surface of stipules, bracts and sepals; they consist of a multicellular and multiseriate central axis of parenchymatous nature, covered by digitiform or sharply pointed epidermal cells of irregular sizes, joined together only in the proximal portion and separated from each other in the distal portion. The columnar cells are axially elongated, with thick cell walls, prominent nucleus and reduced cytoplasm, developed vacuole with lipid inclusions and phenolic compounds. The epidermal cells have thin walls, a conspicuous nucleus, abundant cytoplasm and a poorly developed vacuome. The colleters are devoid of cuticle. The secretion is more abundant in the vegetative apex, impregnating the leaf buds and the stipules, forming a spherical cap that is hard, bright, and hydrophobic. In all analyzed samples, the histochemical assays detected polysaccharides, proteins and lipids in the protoplast of both epidermal and columnar cells; phenolic compounds were detected solely in the columnar cells. The resinous nature of the exudate was confirmed with the use of the diethylic ether solvent. Bacterial leaf nodules were not found.

The formation of the stigmatic surface in Passiflora elegans (Passifloraceae)

“…Colleters secrete a viscous material on the external surface (Thomas 1991;Klein et al 2004;Barreiro & Machado 2007). This process differs from what was observed in this study, as the stigmatic emergences found on P. elegans have pectic compounds in their inner walls.…”

Ultrastructure of secretory and senescence phase in colleters of Bathysa gymnocarpa and B. stipulata (Rubiaceae)

“…occasionally, the middle axis presents vascular bundles (thomas 1991, appezzato-da-gloria & Estelita 2000, Klein et al 2004. in various Rubiaceae genera, the colleters ultrastructure was described recently (Klein et al 2004, miguel et al 2006, Barreiro & machado 2007. several studies reported colleter structure with emphasis on secretory cells, especially in secretion production phase.…”

Estruturas secretoras de mucilagem em Hibiscus pernambucensis Arruda (Malvaceae): distribuição, caracterização morfoanatômica e histoquímica

“…De acordo com Th omas (1991), além da protoderme, células do meristema fundamental e do procâmbio podem estar envolvidas na formação de coléteres, sendo mais raros aqueles originados exclusivamente de células protodérmicas. Coléteres com origem mista foram descritos por Da Cunha & Vieira (1997), Klein et al (2004), Barreiro & Machado (2007) para espécies de Rubiaceae e por Appezzato-da-Glória & Estelita (2000) para espécies de Apocynaceae. Coléteres com origem exclusivamente protodérmica foram registrados por Paiva & Machado (2006a) em Hymenaea stigonocarpa (Fabaceae) e por Paiva & Martins (2011).…”

“…As referidas substâncias são comumente relatadas como fazendo parte da secreção produzida por coléteres de diferentes taxa (Kronestedt-Robards & Robards 1991; Th omas 1991; Appezzatoda-Glória & Estelita 2000; Rio et al 2002;Klein et al 2004;Paiva & Machado 2006a,b;Barreiro & Machado 2007), sendo geralmente a mucilagem o principal componente da secreção, conforme registrado nos coléteres de H. pernambucensis.…”

“…A natureza mucilaginosa da secreção produzida pelos coléteres em órgãos em desenvolvimento tem sido associada com a função de lubrifi car e evitar a dessecação de gemas (Uphof 1962;Fahn 1979;1990;Kronestedt-Robards & Robards 1991;Th omas 1991), local onde são encontrados meristemas em início de desenvolvimento, além de proteger contra patógenos e herbívoros (Fahn 1979;Robbrecht 1988;Kronestedt-Robards & Robards 1991;Paiva & Machado 2006a,b;Barreiro & Machado 2007). Klein et al (2004) detectaram, além de carboidratos, a presença de proteínas na secreção dos coléteres de Simira glaziovii (Rubiaceae), as quais possivelmente estão associadas com mecanismo de defesa contra microorganismos.…”