Fall foliage has been stripped from the trees by fall rains and winter winds. The leaves lie on the ground with remnant colours of yellow, red, orange, brown and hints of green. All the deciduous trees have prepared for winter and the chemistry of fall is done.
Chlorophyll, the green pigment in the chloroplasts of leaves that uses sunlight to produce carbohydrates and sugars for the tree, constantly breaks down with exposure to sunlight and is replaced during spring and summer. Once nutrient flow to the leaves is blocked, chlorophyll replacement stops and the green colour disappears.
The remaining chloroplast pigments, which are much less abundant but more stable than chlorophyll, become visible as the chlorophyll disappears.
Yellow xanthophylls and carotenoids,that reflect light spectra and facilitate the function of chlorophyll, show through. The sugars remaining in the leaf are manufactured into red anthocyanins adding to the range of colours.
You can separate out these different pigments at home. Collect a number of similar coloured leaves; press into the leaves with a straight edge (coin, ruler, screw driver) making a stain along a line near the bottom of a filter paper (coffee filter); place the bottom tip of the filter paper in rubbing alcohol inside a drinking glass; watch the solvent move up the filter paper separating the different pigments as it moves up the paper; remove the filter paper before the solvent reaches the top and let it dry.
Watch these videos on methods to try at home.
Tree Chlorophyll Chromatography
Paper Chromatography Explained
MOSAiC article “Pigments of Fall” Mosaic – Pigments of Fall – Dec 2013