Regulation of in vitro callogenesis and organogenesis from Albizzia root explants by carbohydrate source modifications

Summary Albizzia julibrissin root expiants were used as a model to study the influence of eight carbohydrate sources: arabinose, fructose, galactose, glucose, lactose, maltose, sucrose and xylose on the regeneration capacities in a hormone-free MS medium. Morphological and cytohistological investigations suggested the existence of an antagonism between the callogenic and the caulogenic potentials of a given carbohydrate. The callus stimulator sugars (fructose, glucose and sucrose) were detrimental to the development of the neoformed shoot buds which accumulated great amounts of starch and embarked upon callogenesis. In the presence of less callogenic sugars (maltose, lactose and overall xylose) the majority of neoformed buds gave rise to well elongated and healthy leafy shoots, ready to be used, after rooting, for Albizzia propagation. Galactose proved to be a toxic component in our experimental conditions. It was surprising to find that sucrose, the universally used carbon source in plant tissue culture media, was not suitable in the Albizzia system. The role of starch accumulation in the observed responses is discussed.