What causes leaves to change colour?
Leaves contain a complex mixture of pigments which give a species its characteristic colour. The presence of each is determined by the plants genes and the environment that the plant is in. Most of the pigments in the leaf are masked during the growing season by the green pigment Chlorophyll, so that in most cases the colour we usually see during the spring and summer months is some shade of green. Chlorophyll is hugely important to all plants, as it is the main pigment responsible for capturing sunlight and using the resulting energy to manufacture food for the tree simple sugars (carbohydrates) – which are produced from water and carbon dioxide. During this process, the chlorophylls are broken down and used up, but are also being continually replaced by the tree, so that the foliage stays green. Deciduous trees and shrubs loose their leaves in autumn through a process called ‘senescence’. In late summer, as days become shorter and nights are cooler, chemical changes take place that g
