AUTUMN ANSWERS
Dear HIW,
Autumn is my favourite season, and I was wondering what makes the autumn colours? Nathaniel Mills
The two main pigment types that are visible in leaves are chlorophyll and carotenoids. Chlorophyll gives a green colour to leaves, mostly in spring and summer. This is the stronger pigment, preventing carotenoids from being seen. But chlorophyll needs to be replenished regularly, and nutrients are required to do so. During autumn and winter, the nutrients being transported to the leaves are blocked and the chlorophyll begins to fade. Instead, the yellow and orange carotenoids have their time to shine – at least until the leaves fall.