Effet de l'osmolarité et de la composition du milieu sur la callogénèse,la caulogénèse et la rhizogénèse de fragments d'hypocotyles deBrassica oleracea L. var.botrytis

Callus formation by fragments of cauliflower hypocotyls was favoured by raising culture medium osmolarity above ?0.38 MPa. Increase in sucrose concentration while diminishing macronutrients inhibited callus initiation and growth. Root formation by the same material required a low medium osmolarity (?0.19 MPa). Reducing sucrose concentration in the classical Murashige and Skoog rooting culture medium favoured root formation. Adventitious bud formation was also depending upon medium osmolarity besides the need for a cytokinin. Reducing too much the osmotic potential of the medium had an unfavourable effect on bud neoformation. The importance of sucrose in all these processes is pointed out.