Estudos anatomicos e ultra-estruturais da organogenese in vitro de Passiflora edulis Sims f. flavicarpa Deg / Anatomy and structural studies of in vitro organogenesis of Passiflora edulis Sims f. flavicarpa Deg

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

Meristemoids are responsible for the in vitro organogenesis expression. They may be formed from the explant (direct organogenesis) or from callus (indirect organogenesis). Once in vitro organogenesis is a prerequisite for developing micropropagation strategies and genetic transformation in plants, the ultrastructural analysis of the cells involved in such regeneration provides basic information that optimize protocols. In this context, FB - 100 population of Passiflora edulis Sims f. flavicarpa Deg. was evaluated as to the meristemoids differentiation, the source of explant and the coconut water supply to the culture medium. Meristemoids were analysed from leaf and hypocotyledonar explants cultured in MS medium supplemented with 1.0 mg L-1 BA and 5% coconut water. The histological analyses of the hypocotyledonar explants showed that meristemoids arose from epidermal and subepidermal layers. Meristemoids originated leaf primordia and, sometimes, buds. In general, meristemoids continued dividing, forming protuberances. Such protuberances consisted of meristematic epidermal and subepidermal cells, as well as central parenchymatic cells, although only peripheral layers of the protuberances originated buds. In leaf explants, this process was similar to the processes described for hypocotyledonar explants. However, epidermal and subepidermal layers of protuberances on leaf explants were not well-defined and the number of buds originated from leaf explants was significantly smaller than the number of buds from hypocotyledonar explants. Structural and statistical evaluations confirmed that the hypocotyledonar explants were better than leaf explants. Hypocotyledonar explants developed a callus in the cut region surface. Peripheral layers of the callus formed meristemoids that gave rise to leaf primordial and buds, or continued dividing to form protuberances. This work characterized the ultrastructure of protuberance cells originated directly on the hypocotyledonar explants, as well as those originated on callus. Meristematic cells of direct protuberances showed spherical nucleus. On the other hand, in indirectly-formed protuberances the nuclear envelope showed a large number of nuclear pore complexes, deep invaginations and nuclear fragmentation characterizing the amitotic process. Analyses under scanning electron microscope of the hypocotyledonar explants cultured on MS medium supplemented with 1.0 mg L-1 BA and either with or without 5% coconut water did not evidence structural differences between buds and protuberances. The quantitative evaluation demonstrated that coconut water was efficient to increase the number of buds.

ASSUNTO(S)

amitose histology histologia amitosis morphogenesis maracuja passionfruit morfogenese

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