The leaves of higher plants contain various types of photosynthetic pigments. Chlorophylls exist in two forms—chlorophyll a and b—both of which are green. Carotene is an orange-yellow pigment that is also abundant in carrot roots, and several xanthophylls range from shades of yellow to almost colorless, depending on their molecular structure. A-B. Chlorophyll molecules break down in autumn, unmasking the yellow carotene and xanthophylls in leaves. Some, such as those of liquidambar (left), turn red when anthocyanin pigments add the final touch to the tree’s colorful spectacle.
