No abstract

Few ultrastructural differences were noted among the three species. These secretory structures not only protect the shoot apex, but also have taxonomic importance below the genus level.

-(ultrastructure of secretory and senescence phase in colleters of Bathysa gymnocarpa and B. stipulata (Rubiaceae)). Colleters are secretory structures formed by a parenchymatic axis with vascular bundles, bound by a layer of secretory palisade-like epidermis. some studies regarding the structure of colleters have focused on secretory cells structure, but not distinguished the secretory and senescent phases. generally, in mucilage-secreting cells such as colleters, the endoplasmic reticulum and golgi apparatus are involved in secretion production and transport. in these study, colleters structure of Bathysa gymnocarpa K. schum. and B. stipulata (Vell.) C. presl. (Rubiaceae) were determined in two phases: a secretory phase and a senescence one. samples were collected and processed by usual light and electron microscopy techniques. studied colleters are constituted by an epidermal palisade layer and a central axis formed by parenchymatic cells with rare vascular traces. during the secretory phase, epidermal cells presented a dense cytoplasm, small vacuoles, enhanced rough and smooth endoplasmic reticulum, and a golgi apparatus close to large vesicles. during the senescence phase epidermal cells presented a disorganized membrane system. no intact organelles or vesicles were observed. the outer cell wall exhibited similar layers to that observed during the secretory phase. The senescent phase is easily defined by the morphology of the colleters, but not well defined at subcellular level. our research suggests that programmed cell death starts on secretory phase. however, more evidences are needed to evaluate the phenomena.Key words -light and electron microscopy, plant cell ultrastructure, programmed cell dead, secretory structure RESUMO -(ultraestrutura da fase secretora e da senescente dos coléteres de Bathysa gymnocarpa e B. stipulata (Rubiaceae)). Coléteres são estruturas secretoras formadas por um eixo parenquimático que inclui feixes vasculares, circundado por uma camada de células epidérmicas secretoras em paliçada. Em estudos sobre a estrutura dos coléteres tem sido observada a ultraestrutura das células secretoras, mas não discriminam as fases secretora e senescente. geralmente, em células secretores de mucilagem como os coléteres, o retículo endoplasmático e o complexo de golgi estão envolvidos na produção e no transporte da secreção. neste estudo, foram determinadas duas fases baseadas na estrutura dos coléteres de Bathysa gymnocarpa K. schum. and B. stipulata (Vell.) C. presl. (Rubiaceae): a fase secretora e a fase senescente. amostras foram coletadas e processadas utilizando técnicas usuais de microscopia óptica e eletrônica. os coléteres estudados são constituídos por uma camada epidérmica em paliçada e um eixo central parenquimático com traços vasculares raros. durante a fase secretora, as células epidérmicas se apresentam com o citoplasma denso, pequenos vacúolos, retículo endoplasmático liso e rugoso evidente e complexo de golgi próximo a grandes vesículas. durante a fase senescente, as cél...

Heterostyly is a genetically controlled floral polymorphism usually associated with an incompatibility system. This set of features is known to occur in several angiosperm families, but some aspects of its biology has not been well studied. The present study investigates cellular aspects of the pollen-pistil interaction after compatible and incompatible pollinations of Psychotria nuda, to increase our knowledge of heteromorphic self-incompatibility (HetSI). The use of bright field, fluorescence and transmission electron microscopy methods allowed us to demonstrate that pollen tubes behave differently after incompatible and compatible pollinations. Pollen tubes were particularly distinct after incompatible pollinations of L- and S-morph flowers. Relative to compatible pollen tubes, incompatible L-morph tubes had a drastic reduction in cellular contents, but no cell rupture. Incompatible S-morph tubes exhibited dense cytoplasm in apical regions, as well as in other regions, accompanied by a rupture of the apex. These results support the hypothesis that L- and S-morph flowers have different incompatibility mechanisms during HetSI.