Anatomia da origem e do desenvolvimento de raízes adventícias em estacas do maracujazeiro amarelo (Passiflora edulis Sims forma flavicarpa Degener)

Resumo

The object of this study was to describe rooting of washed and unwashed cuttings from various parts of the stem of the passion fruit, Passiflora edulis Sims f. flavicarpa Degener.

Cuttings from apical, median, and basal portions of the stem were used. The bases of the cuttings were immersede in running tap water up to the middle of the second internode for 36 hours; after that treatment, those cuttings, along with the controls, were struck in Wooden boxes containg sterilized sand and were placed under intermittent mist. Every 5 days after striking some of the cuttings were taken up for histological observation. The root primordia originate in two distinct regions: a) in the callus lump formed at the base of the cutting and b) endogenously along the wood rays. In the first case the formation of the anatomic structure of the root primordium is initiated by the progressive differentiation of callus cells in the vicinity of the vascular elements. The development of the root primordium continues endogenously in the direction of the wood ray and exogenously toward the end of the sectioned material, creating in this way the connection between the developing tissues and corresponding ones in the stock. In the second case the mitotic activity of the cells of pericycle located along the wood rays was stimulated, the outline of this root primordium then appearing in this region, developing equally in centripetal and centrifugal directions, and establishing in this manner the connection of tissues of the developing organ with corresponding ones in the stock. It was determined that washing of the cuttings promoted a more evident and pronounced initial development of roots and that the apical portion of the stem was the one which responded best to washing.