Pigments Found in Green Plants

Chlorophyll

• Chlorophyll is found in all green plants and most forms of algae, according to information from Westfield State University in Massachusetts. Chlorophyll contains a "head," called a porphyrin and a "tail," which is called phytol. Chlorophyll reacts to sunlight; therefore, when there is a lot of sunlight, the leaves are green. When there is less sunlight, leaves produce less chlorophyll and begin to lose their green color. This is why leaves change their color in the fall.

Carotenoid

• Unlike chlorophyll, the pigment carotenoid does not rely on sunlight. This pigment is always found in some leaves no matter what the season. There are two types of carotenoids and these are the same pigments that give some orange and yellow vegetables, such as squash and carrots, their color. Red comes from lycopene and xanthophyll produces a yellow color. Some leaves have so much carotenoid that they may seem yellow, even in the summer.

Flavonoids

• The flavonoids are important pigments in creating the color changes seen in autumn. Yellow is found in flavone and flavol while anthocyanins can be red, blue or purple. If a plant has a purple color, it is likely due to the anthocyanins. The anthocyanins are called a natural sunscreen for plants, too. If the soil is very acid, it can also affect the color of the anthocyanin in the leaves, which may explain why some trees have yellow leaves in the fall in some areas and the same type of tree may not have yellow leaves in other areas.

Chemicals and Leaf Color

• Sometimes leaf color is not due to any type of pigment but because of chemicals reacting to the pigment. Oak trees, which are prevalent in many areas of the United States, contain tannins, which cause some leaves to turn brown. Tannins are also found often in the leaves of the walnut tree. However, brown leaves do not necessarily mean that tannins are present. Most often leaves turn brown because the leaf is dying or has already died.