Chlorophyll is the molecule found in green plants that absorbs sunlight necessary for the process of photosynthesis for the sustenance of plant lives. Situated in the chloroplasts of green plants, it is what constitutes the green color of green plants. When light falls on plants, chlorophyll pigments take in blue light and some quantity of red light while the reflection of other colors takes place which ends up in the production of green color that we commonly relate to green plants.
Chlorophyll pigments are situated in and around photosystems, which are pigment complexes of protein fixed in the thylakoid membranes of the chloroplasts. The purpose of the greater part of the chlorophyll is to take in light energy and channel it by resonance transfer of energy to a particular pair of chlorophyll at the photosystems center of reaction. Chlorophyll pigments are particularly selective concerning the wavelength of light they infiltrate; therefore, parts of the leaf region having the pigment are seen as green. The reaction center complexes have the ability to absorb photosynthetic light directly and take part in the events of the separation of charges devoid of the chlorophyll molecules. However, the chances of cross-section (the possibility of a photon infiltrating within a certain intensity of light) are limited. Therefore, the rest of the chlorophylls in the photosystem and the antenna-molecule protein complexes linked with the photosystems all collaboratively take in and channel light energy to the reaction center. In addition to chlorophyll a, accessory pigments are found in these antenna-molecule protein complexes (Gunning & Steer 22).
Carotenoids are a cluster of yellow, orange, red, or brown pigments present in a wide range of living things, especially in the chloroplasts of most plants. Carotenes (contain oxygen molecules), and xanthophylls (lack oxygen and are hydrocarbons) are the main types of carotenoids. All of them occur as long-chain lipids components. In the process of photosynthesis, a number of carotenoids act as accessory pigments (“Carotenoid” para. 1-2). They absorb photosynthetic light and save the chlorophyll molecules from photodamage.
Anthocyanins are water-soluble molecules that come into view as red, blue, or purple depending on the structure and the plant’s acidic conditions. They are mainly red at high conditions of acidity and change into blue at conditions of low acidity. Their color is also dependent on conditions of temperature, the presence of oxygen, UV light, and various other co-factors. Anthocyanins serve the purpose of protecting plants from harmful UV light.
Plants absorb light energy by the use of chlorophyll; consequently, they are seen as green. However, what normally happens in the fall when leaves change their colors? Why are there so many different colors such as yellow, orange, and red? This phenomenon can be attributed to plants containing other pigments that include carotenoids (yellow-orange), and anthocyanins. These accessory pigments are contained in the leaf together with the chlorophyll pigments and they are the basis for the many different shades of green in plants. The colors intensity varies in some years depending on the concentration of the accessory pigments in the leaves. Chlorophyll envelops them for most of the period in summer, but during the fall, when most plants start to anticipate the forthcoming winter conditions and become dormant, the plant cells bring to an end the production of chlorophyll. Therefore, the green coloring of the leaves is lost (“What is photosynthesis?” para.10). The carotenoids and anthocyanins found in the leaves are unmasked to demonstrate their different colors.
Works Cited
“Carotenoid.” The Free Dictionary. 2009. Web.
Gunning, Brian E., and Steer, Martin W. “Plant cell biology: structure and function.” Toronto: Jones and Bartlett Publishers. 1996. Print.
“What is photosynthesis?” Biology, Answering the Big Questions of life/Photosynthesis. 2009. Web.