THE DIFFERENTIATION OF PIGMENTATION IN FLOWER PARTS. III. METABOLISM OF SOME EXOGENOUS ANTHOCYANINS BY DETACHED PETALS OF IMPATIENS BALSAMINA

The anthocyanins of mature petals of Impatiens balsamina L. are distinct from the pigments found in vegetative tissue. In the red genotype (llHHPrPr) a sequential elaboration of the characteristic anthocyanins has been previously demonstrated through the examination of buds at successive stages of development. The metabolism of anthocyanins, especially pelargonidin-3-monoglucoside, was examined by infiltration into developing petals of a genetically white strain. This anthocyanin appears to play a central role in the biochemical sequences involved and it has been observed that the genetically white flowers possess the enzymatic potential to metabolize this substrate, producing the same final products which are produced in the red genotype. There is a pattern of change in the relative amounts of each anthocyanin during the incubation period which follows closely the pattern which occurs during normal development of the colored genotypes. This indicates that the enzymes which are normally produced in the colored flowers are also produced in flowers which never produce anthocyanins. The metabolic capabilities of several other genetic strains and the influence of light and puromycin have been examined. IN A SERIES of studies on the red genotype (IlHHPrPr) of Impatiens balsamina L., Hagen (1966 a, b) has demonstrated that there is a sequential elaboration of the characteristic anthocyanins during morphogenesis of the flower buds. This work has provided a partial description of the morphogenesis of a molecule, a developmental sequence which is apparently part of the differentiation of the flower and subject to controls similar to those which regulate other aspects of differentiation. Past attempts to demonstrate the sequential modification of a particular flavonoid compound in flower petals have been inconclusive (Suomalainen and Kerhnen, 1961), although Hess (1964) has demonstrated that there is a sequential production of different anthocyanidins during bud maturation in petunia. The production o pigmentation in petals from flower buds of Impatiens balsamina L. may be divided into four periods (Hagen, 1966b). The first period is characterized by the absence of anthocyanins, although other flavonoid compounds are present In the second, pelargonidin3-monoglucoside appears and is apparently followed by a smaller quantity of the corresponding aglycone. The third period is one of rapid synI Received for publication September 20, 1965. This investigation is a portion of a dissertation presented to the Graduate School of Indiana University, Bloomington, in partial fulfillment of the requirements for the degree Doctor of Philosophy (1964). This research was supported in part by National Science Foundation Grants G-6138 and G-21943 awarded to Dr. Charles W. Hagen, Jr. 'Present address: United States Air Force School of Aerospace Medicine, Brooks AFB, Texas. thesis during which the final products first appear but are accompanied by a confusing wealth of intermediate forms. In the final stage which begins with anthesis, the compounds of intermediate complexity disappear, leaving a mature flower pigmented with acylated-3,5-diglucosides and the other highly substituted forms of pelargonidin. While this sequence of developmental events suggests a corresponding biosynthetic sequence, there remains confusion concerning the route or routes actually followed during normal flower development. It is impossible from descriptive studies to distinguish those products which are necessary precursors of the final pigments from those which may be accidental by-products or components of secondary pathways. To test the synthetic capabilities of the intact petals, techniques were developed for administering potential substrates to cultured petals. Where the substrates could be prepared in forms compatible with and made available to the intact petals, modification of the substrate provided further information concerning the biosynthetic pathway and the developmental mechaniisms which regulate this pathway. MATERIALS AND METHODS-A dministration of substrate-Plants of the garden balsam, Impatiens balsamina L., were employed in this study. The genotypes used were llHHpp (pink), llhhPrPr (pink), llHHPrPr (red) LLhhPrPr (purple) and llhhpp (white) as originally designated by Davis, Taylor, and Ash (1958). Stage-3 buds (Fig. 1), as defined by Hagen (1966b), were most frequently used as test objects because the descriptive studies had indicated that biosynthetic systems were