Question

Leaves change colour in autumn. Why?

Answer 1

Leaves are usually green in colour due to the presence of chlorophyll pigment. The pigments of other colours are also present in leaf but remain covered by chlorophyll. Light regulates the production of chlorophyll. As in autumn days become shorter, the supply of sunlight reduces. The chlorophyll production also reduces, so the green colour starts fading from the leaf. Meanwhile other pigments start expressing their colour. As a result the leaves become red (anthocyanine), yellow or orange (carotenoid).