KNOWN FACTORS RESPONSIBLE FOR INFINITE FLOWER COLOR VARIATIONS

Anthocyanins, the compounds generally considered responsible for most pink through blue flower color, are virtually colorless within the pH range of approximately 4 to 6. Since the pH of epidermal cells of most flowers is within this range, it is most improbable that anthocyanins per se significantly contribute to the color of most flowers.
Metals, such as iron and aluminum, chelate with anthocyanins that contain an ortho-dihydroxyl system to form highly colored, stable metal complexes, but there is little evidence that this reaction occurs in nature.
Other flavonoids and related compounds can associate with anthocyanins and form colored anthocyanin-copigment complexes that are stable at pH’s where anthocyanins alone are virtually colorless.
The colors and color enhancement caused by the formation of anthocyanin-copigment complexes are greatly influenced by pH, concentration of anthocyanin, and the molar ratio of copigment to anthocyanin.
Since copigmentation occurs with glycosides of all six commonly occurring anthocyanidins, this phenomenon offers a logical explanation for the inconsistency that has existed between the known chemical behavior of anthocyanins and the infinite flower color variations from pink to blue that occur naturally.

I International Symposium on Floriculture Plant Breeding and Genetics

S. Asen

https://doi.org/10.17660/ActaHortic.1976.63.27