Differential Regulation of Flavone Glycosylation during Ontogeny of Silene pratensis

Two isovitexin glycosides have been found in the cotyledons and foliage leaves o f Silene pratensis plants that are unable to glycosylate isovitexin in their petals (genotype gg glgl fgfg). The glycosides (isovitexin 7-O -galactoside and isovitexin 7-O -galactose 2 " -0 -a rab in o sid e ) were present only in the lower leaves: leaves p roduced later in the developm ent o f the flower stem accumulated only the aglycon isovitexin. The transition in the flavone com position during the ontogeny of the plants could be influenced by light intensity. In plants grown at low light intensity, glycoside p roduction continued until a h igher lea f p a ir n u m b er than in plants grown at higher light intensities. However, the effect o f light intensity is indirect: the transition in the flavone com position is correlated w ith the transition from rosette leaves to stem leaves. The presence of the 7-O-galactosides in cotyledons and rosette leaves suggests th a t in add ition to the g, gi and fg loci, there are fu rther glycosylating loci w hich are not expressed in stem leaves and petals.