ISHS Acta Horticulturae 78: Symposium on Tissue Culture for Horticultural Purposes
HORTICULTURAL AND PHYSIOLOGICAL ASPECTS OF CITRUS BUD CULTURE |
| Authors: | A. Altman, R. Goren |
| Abstract:
The study of bud development of perennial plants is fraught with difficulties since the bud forms a distinct physiological unit with a differentiating meristem of its own but, at the same time, is dependent on physiological events in other organs of the tree. The culture of isolated buds offers a possibility of overcoming some of these difficulties and of a better elucidation of the role of growth regulators and environmental conditions in bud development. This approach was attempted in Citrus sinesis (L.) Osbeck, and appropriate aseptic methods for in vitro culture of isolated buds and callus tissue have been devised. Buds excised from mature or juvenile trees were cultured on defined media for prolonged periods, sprouted, and proceeded with their vegetative development in vitro. The annual growth rhythm of buds was determined, and an innate dormancy, which was dependent on the balance of IAA, GA and cytokinins, was revealed. Defoliation and photosynthate-starvation of the mother-plants affected subsequent growth of bud explants in vitro. Abscisic acid, as well as omission of sucrose from the medium, stimulated callus formation in the abscission zone of the leaf, but high levels of sucrose were required for the growth of shoots. Exogenous ethylene was found to stimulate callus formation, while evolution of endogenous ethylene was dependent on the type of explant and on the composition of the medium. The metabolic and physiological competence of the buds was evaluated in terms of their ability for uptake of sucrose, protein synthesis and ethylene evolution. The significance of the various developmental events which occur in bud cultures is discussed in relation to similar events in the intact tree. | |
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