Anthocyanin Synthesis: 10 Times More in Grapes Exposed to the Sun

Luminosity and temperature are the main environmental variables that regulate the synthesis of anthocyanins; Luminosity stimulates it, while high temperatures seem to inhibit it. In the phenological phase of ripening, exposed to the sun, bunches of grapes contain up to 10 times more anthocyanins than shaded ones.

Source: del Valle Leguizamón, G., León, A. G., & Sañudo, R. B. (2005). Anthocyanins in grapes (Vitis vinifera L.) and their relationship with color. Revista Fitotecnia Mexicana, 28(4), 359-368.