Carotenoids are present in leaves the whole year round, but their orange-yellow colors are usually masked by green chlorophyll.

When it is serious, spots and patches of yellow and red appear as the green chlorophyll is not made, or breaks down.

Photosynthesis uses the green colored chlorophyll and only needs light, carbon dioxide from the air and water to operate to make sugars (carbohydrates).

The glow is the result of chemical that is created as the green chlorophyll in the peel breaks down.

Maybe the plants will find some superefficient yellow pigment that's better than green chlorophyll.

When leaves change color in the fall, it is due to the loss of green chlorophyll, which unmasks preexisting carotenoids.

In photosynthesis, energy from sunlight is absorbed by green chlorophyll in plant cells called chloroplasts.

This process also stops the production of the dark green chlorophyll to replace the chlorophyll that deteriorates naturally in sunlight.

The removal of the green chlorophyll unmasks the red, gold and brown pigments which leaves also contain, creating the beautiful hues of autumn.

Each year, he said, the trees follow the same pattern as the green chlorophyll ebbs from leaves and reveals the colors below.