Glycerol and myo-inositol as carbon sources for the induction of xylogenesis in explants of Lactuca

Abstract

Glycerol (2% w/v) and myo-inositol (2% w/v), respectively, functioned as the principal exogenous carbon source for the induction of tracheary element differentiation in cultured expiants of lettuce pith (Lactuca sativa cv. Romána). Although tracheary elements were first observed after 3 days on a xylogenic medium supplemented with either glucose (2% w/v) or myo-inositol (2% w/v), the induction of xylogenesis in explants cultured on a similar medium containing glycerol (2% w/v) required a minimum of 6 days. Tracheary elements formed in the presence of glycerol and myo-inositol, respectively, were characterized by various patterns of scalariform-reticulate secondary wall thickenings which were indistinguishable from tracheary elements produced under similar cultural conditions in the presence of glucose as the principal carbon source. This is the first report of a major exogenous carbon source other than a carbohydrate supporting the cytodifferentiation of tracheary elements under in vitro conditions.