What causes autumn color changes in plants?

Autumn color changes in plants are predominantly caused by photoperiod changes, which refer to the varying lengths of day and night as the seasons transition from summer to fall. As daylight decreases, plants receive signals that trigger the breakdown of chlorophyll, the pigment responsible for the green color in leaves. This chlorophyll breakdown reveals other pigments that have been present all along but were masked by the green of chlorophyll.

Carotenoids, for example, produce yellow and orange hues, while anthocyanins contribute to red and purple colors in some species. The change in length of daylight is a critical factor in this process, as it helps regulate the physiological changes in plants that lead to leaf senescence and color transformation. The combination of temperature and moisture also plays a role in the intensity of these colors, but the fundamental trigger for the color change is the photoperiod.