Red Phenotypes (homozygous dominant)

SHIKIMIC ACID PATHWAY
         |
         |
         V          AA genotypes       cyanidin             cyanidin
  DIHYDROQUERCETIN ---------------> 3-arabinoside -----> 3-diarabinoside
         |          (high enzyme
         |           activity)
         |
         V
     QUERCETIN-----> monoside -----> diglycosides -----> triglycosides
                       (low)            (high)               (low)

Pink Phenotypes (heterozygous)

SHIKIMIC ACID PATHWAY
         |
         |
         V          Aa genotypes       cyanidin 
  DIHYDROQUERCETIN ---------------> 3-arabinoside
         |          (low enzyme        reduced
         |           activity)
         |
         V
     QUERCETIN -----> monoside -----> diglycosides -----> triglycosides -----> tetraglycosides
    (increased)       (medium)          (medium)            (medium)                (low)

Yellow Phenotypes (homozygous recessive)

SHIKIMIC ACID PATHWAY
         |
         |
         V          aa genotypes       
  DIHYDROQUERCETIN ---------------> no anthocyanadin production 
         |          (no enzyme
         |           activity)
         |
         V
     QUERCETIN -----> monoside -----> diglycosides -----> triglycosides -----> tetraglycosides
  (high increase)
                       (low)            (medium)               (low)                (low)
Figure 10. Proposed synthesis pathway for observed floral differences in T. sessile (from Les et al., 1989).