The Differentiation of Pigmentation in Flower Parts, IV. Flavonoid Elaborating Enzymes From Petals of Impatiens balsamina s

Abstract

Extracts of the flower petals of Impatiens balsamina L. contain enzymes which catalyze the glycosylation of phenolic compounds. Enzymes have been extracted which glycosylate hydroquinone to arbutiiw and at least 3 different flavonols to the 3-monoglucoside. The hydroquinone glucosylating enzyme is similar to enzymes previously described except that it requires an unidentified low molecular weight oofactor. The glucosylation of flavonols follows normal enzyme kinetics; it requires a nucleotide diphosphate glucose donor for activity, and is made more evident by the presenoe of gluoono-1:5S4actone, an inhibitor of endogenous glucosidases. It is suggested that the flavonol glucosylating enzyme acts naturally to gluco-sylate a precursor of both flavonols and anthocyanins to the 3-monoglucoside. The only elaboration of an anthocyanin observed with petal extracts was an acylation of pelargonidin-3-monogluooside. Hagen (7) has examined the flavonoid compounds in the flower parts of the red-flowered genotype (1 1HHPrPr) by paper chromatography and has found the largest variety of anthocyanidins and flavonols in the stem: a more limited variety in the sepals; and only 1 anthocyanidin, pelargonidin, and 1 flavonol, kaempferol, in the petals. The pigments of the petal, however, are the most highly substituted, with diglucosides, acylated diglucosides and glucose biosides present. The mature sepals and the stems do not show this type of flavonoid elaboration ; only monoglucosides are present. This represents a progressive reduction of the number of types of flavonoids but an increase in the substitution in the progression from vegetative to reproductive tissue. Therefore, the differential distribution of these highly substituted pigments in the flower parts provides a tool with which factors controllin,g flower differentiation may be studied. Since a function can be assigned to these pigments in the petal (7), they should be under some of the same developmental controls as petal morpogenesis but could be more readily analyzed than structural features. Hagen (8) has also shown that during the development of the red petal a progressive elaboration of the anthocyanins takes place. He has divided the time of development into stages according to 1 This paper has been dedicated to Professor Ralph E. Cleland on the occasion of his seventy-fifth birthday in recognition of the stimulation and academic guidance which he has provided for both authors.