Adventitious rooting of apple microcuttings in vitro: an anatomical study

Abstract

In view of the lack of information on the anatomy of rooting in vitro, the time course of adventitious rooting was followed in an apple rootstock. Microcuttings raised on Murashige–Skoog medium were transferred to medium containing indolebutyric acid, then fixed at 0, 1.5, 3, 5, 7, and 10 days. A variety of tissues in close proximity to the cut stem surface exhibited an "activation" response over the first 3 days. Root meristemoids consisting of densely staining cells with enlarged nucleoli formed outside the xylem by day 5. Considerable variation in meristemoid development was noted within single stems and among stems. Meristemoids transformed into root primordia, some of which established a vascular connection with the stem by day 10.

Anatomical and biochemical changes during root formation in oak and apple shoots cultured in vitro

“…Similar findings were reported by Hicks (1987), who observed that in apple the tissues in and around the vascular strands became activated, and that meristemoids formed from certain of these cell populations lying outside the xylem.…”

“…This approach has already been applied in studies on the development of adventitious roots by apple microcuttings (Hicks, 1987;Zhou et (Jensen, 1962 Torrey's (1966) (fig 3c). By d 5-6, the meristemoids had begun to become individualized, the plane of cell divisions giving rise to the typical pointed shape of the root primordium.…”

Root histogenesis in herbaceous and woody explants cultured in vitro. A critical review

“…For instance, in Malus domestica 'Jork 9' cuttings, primary modifications occur in the cortical parenchyma, while the meristemoids are set up in the interfascicular region (Auderset et al, 1994). Since activation exists only a few millimeters from the cut surface, it has been suggested that wound factors play an important role, at least at the beginning of the rhizogenic process (Hicks, 1987).…”

Factors affecting adventitious root formation in microcuttings of Malus

“…This may be explained by the photodegradation of IBA in the light (Van der Krieken et al, 1992 (Davis and Haissig, 1990) and the reduction of rooting by cytokinins (Van Staden and Harty, 1988) are well known. Gibberellins, abscisic acid, polyamines, ethylene, brassinosteroids and jasmonic acid have inconsistent effects or have only infrequently been examined (Davis and Haissig, 1990 (Hicks, 1987 (Hicks, 1987 propagation in vitro offers an excellent possibility to study which factors determine the rooting ability of a shoot.…”