PHENOLIC SUBSTANCES 205 



common to all the pigments. A similar type of competition is reported 

 in Primula (de Winton and Haldane, 1933). In Impatiens balsamina, 

 the gene L allows production of malvidin type anthocyanins and also 

 the related flavonol, myricetin (Clevenger, 1958), yet there does not 

 appear to be competition between anthocyanins and flavonols in this 

 plant since a fifty-fold increase in pelargonidin content of flowers does 

 not reduce appreciably the amount of its flavonol analog, kaempferol 

 (Hagen, 1959). A dominant gene which effects production of two 

 different classes of 3':4':5'-trihydroxylated pigments is known in 

 Solanum phureja and also in Primula sinensis. In Dianthus a dominant 

 gene, R, introduces cyanidin and its flavonol analog, quercetin, while 

 pelargonidin and its analog, kaempferol, occur in the absence of R 

 (Geissman et al., 1956). 



One of the most informative examples of interaction between 

 several classes of flavonoids is that of Antirrhinum (Sherratt, 1958) 

 (Fig. 11-3). The types of flavonoids which occur in Antirrhinum are 

 anthocyanins, flavonols, flavones, and aurones. In most of these classes 

 more than one representative aglycone type is present, though not 

 necessarily together in a single plant. Genetic control of flower color 

 in Antirrhinum has been investigated by several groups independently, 

 and the present discussion is taken from Sherratt (1958) using the 

 genetic symbols of Dayton (1956). A factor, Y, is necessary for the 

 formation of flavonoids. Unless certain other dominant genes are 

 present, however, only pigments of the flavone and aurone types are 

 found (namely, apigenin and aureusidin). In the presence of the 

 double recessive, IaIa, aureusidin content is increased with no 

 apparent reduction in apigenin content. In fact no other factors under 

 consideration appear to affect apigenin. The gene, R, governs simul- 

 taneously the appearance of anthocyanins and flavonols (both classes 

 have a 3-OH in the heterocyclic ring). Gene B governs the substitu- 

 tion pattern of the B ring, introducing dihydroxy rather than mono- 

 hydroxy derivatives in the anthocyanins and flavonols present. Gene B 

 does not affect the other two classes of flavonoids. The interpretation 

 of these data is implicit in figure 11.3. Notably, it appears that the 

 pathway to aurone synthesis is determined rather early. Jorgensen and 

 Geissman (1955) have shown that increased anthocyanin synthesis re- 

 sults in some lowering of the aureusidin content however. 



In Phaseolus a series of alleles, C", C and C' influence relative 

 quantities of flavonols and anthocyanins as well as the substitution 

 pattern of the B ring (Feenstra, 1960). None of these substances is 

 formed in the presence of the recessive, C"; C along with the factor 

 viae results in the formation of flavonols of the kaempferol type plus 

 a small amount of the quercetin type and no anthocyanins; C^^ with 



