Green plants have six closely related photosynthetic pigments (in order of increasing polarity):
Chlorophyll a is the most common of the six, present in every plant that performs photosynthesis. The reason that there are so many pigments is that each absorbs light more efficiently in a different part of the electromagnetic spectrum. Chlorophyll a absorbs well at a wavelength of about 400–450 nm and at 650–700 nm; chlorophyll b at 450–500 nm and at 600–650 nm.
Chlorophyll is the green pigment found in most plants, algae, and cyanobacteria. It is contained in microscopic cell organelles called chloroplasts . Pigments are chemically porphyrin molecules, which have a metal ion at the center. The metal ion in hemoglobin is iron and in chlorophyll, it is magnesium. Chlorophylls absorb light at both ends of the visible spectrum – i.e. BLUE and RED light, and reflect green light. That is why chlorophyll appears green. Chlorophyll helps in absorbing energy from sunlight, which is used during photosynthesis. Chlorophylls are the main pigments as they are involved in the conversion of light energy into chemical energy.
There is another photosynthetic pigment called carotenoid in plants. The carotenoids also absorb light energy but they pass it to the chlorophyll molecules. Chlorophylls are blue–green (chlorophyll–a) or green (chlorophyll– b) in color whereas carotenoids are orange (carotenes) or yellow (xanthophyll). Chlorophyll is highly sensitive to light, but too much light may destroy it.