Hormonal Control of Organogenesis and Somatic Embryogenesis inBeta vulgarisCallus

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Abstract
Tétu, T., Sangwan, R. S. and Sangwan-Norreel, B. S. 1987. Hormonal control of organogenesis and somatic embryogenesis in Beta vulgaris callus.—J. exp. Bot. 38: 506–517. Three main pathways of morphogenesis viz: root formation, shoot formation and somatic embryogenesis, have been observed in the callus derived from various explants of Beta vulgaris L. Growth hormones but not the basal media, determined the morphogenetic potentiality of the callus. Auxin alone induced root formation. A combination of an auxin (naphthalene acetic acid) and a cytokinin (6-benzylaminopurine) gave only infrequent bud formation with very low percentages (a maximum of 12%). Regular bud formation with high percentages (52%) occurred when an anti-auxin (2,3,5-triiodobenzoic acid) with a cytokinin (BAP) was used. Shoots (2–3 cm) were transferred to a rooting medium. Roots were formed readily in about 95% of the shoots. Histological studies showed that callus first formed meristematic zones and then shoot primordia developed in these zones. Somatic embryos were formed only in the calli derived from petiole explants. Multiple hormonal sequences were necessary for the induction and development of these somatic embryos. The embryos developed into normal plants when transferred, at the cotyledonary stage, to a hormone free basal medium.