The Function of Carotenoid Pigments in Photosynthesis and their Possible Involvement in the Evolution of Higher Plants

Abstract

It is well established that carotenoid pigments serve two principal roles in photosynthesis. First, they serve as auxiliary antennae whereby the rate of light absorption by photosynthetic membranes is increased, and second, they serve a photoprotective role by intercepting chlorophyll triplet species and preventing the formation of singlet oxygen $$(^10_2 )$$. In terms of photophysics, antenna function is associated with the absorption of light in the blue-green spectral region by the carotenoid pigment followed by singlet- singlet energy transfer whereby the excitation energy is transferred from the carotenoid pigment to a nearby chlorophyll molecule. Photoprotection involves energy transfer in the opposite direction and of a different type. The donor is the excited triplet chlorophyll molecule, the process is known as triplet-triplet energy transfer, and it results in the production of an excited triplet carotene molecule.