SKIN COLOR IN APPLES - INFLUENCE OF COPIGMENTATION AND PLASTID PIGMENTS ON SHADE AND DARKNESS OF RED COLOR IN 5 GENOTYPES

The biochemical and cytological mechanisms responsible for the differe nces in red color quality of apples (Malus domestica Borkh.) were inve stigated. Copigmentation, the increase in absorbance maxima (lambda ma x) from anthocyanin and flavonoid interactions, is known to be a mecha nism for producing variation in shade of red in flowers. In intact app le skin cells, the mean lambda max was 550 nm, with no significant dif ference between genotypes. Furthermore, the ratio of flavonols and pro anthocyanidins to anthocyanins was similar for all genotypes. Therefor e, copigmentation is not a mechanism producing different shades of red in apples. Darkness of red skin was positively related to the proport ion of red cells in the skin and the size of the vacuoles containing a nthocyanins. Measurements of plastid pigments, chlorophyll, and carote noids, compared with L, a*, b* measurements, indicated that the visua l blending of plastid pigments and anthocyanins has an important influ ence on red coloration of apple skin.