influence of explant orientation and contact with the medium on the pathway of shoot regeneration in vitro in epicotyl cuttings of Troyer citrange

• Published in: Plant cell, tissue and organ culture tissue and organ culture, 2006-05, Vol.85 (2), p.137-144
• Main Authors: García-Luis, A, Molina, R.V, Varona, V, Castelló, S, Guardiola, J.L
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Biotechnology; callus; Citroncirus webberi; Citrus sinensis; culture media; epicotyls; Eukaryotic cell cultures; explants; Fundamental and applied biological sciences. Psychology; gravity; hybrids; in vitro culture; in vitro regeneration; methodology; Methods. Procedures. Technologies; micropropagation; Miscellaneous; organogenesis; Plant cells and fungal cells; Poncirus trifoliata; shoots
• ISSN: 0167-6857; 1573-5044
• DOI: 10.1007/s11240-005-9060-4

The effect of orientation as regards to gravity, and that of contact with the medium of culture, on shoot regeneration at the cut edges of epicotyl explants of Troyer citrange (Citrus sinensis (L.) Osbeck x Poncirus trifoliata (L.) Raf.) have been separated. The shoot regeneration pathway was not affected by the orientation of the explants as regards to gravity, and was determined by explant polarity and the contact with the culture medium. At the apical edge of the explants, the contact with the medium shifted the pathway of shoot regeneration from a direct one to an indirect one, with formation of a callus. This callus formation was cytokinin-dependent, but the change in the pathway of organogenesis was not caused by the increase in cytokinin availability resulting from the contact with the medium. In contact with the media, regeneration at the basal edge of the explants occurred through an indirect pathway after callus formation. No regeneration occurred, at the basal edge, if the contact with the media was prevented. The orientation of the explants as regards to gravity affected shoot formation through the direct pathway of organogenesis. The number of buds differentiated, and that of growing shoots increased when the orientation of the explants departed from the vertical upright position.