Which pigment class helps protect photosystems by dissipating excess light energy as heat?

Which pigment class helps protect photosystems by dissipating excess light energy as heat?

• A. Carotenoids
• B. Chlorophyll a
• C. Chlorophyll b
• D. Anthocyanins

Answer: (A)

Carotenoids provide photoprotection by dissipating excess light energy as heat. As accessory pigments in the light-harvesting complexes, they can accept energy that would otherwise overexcite the reaction centers and release it as heat instead of letting it form reactive species. Under high light, the xanthophyll cycle adjusts the pigment composition to boost this non-photochemical quenching, helping to shield photosystems from damage by quenching excited states and preventing the formation of triplet chlorophyll and singlet oxygen. Chlorophyll a and chlorophyll b are the main light absorbers that funnel energy to the reaction centers, not the primary dissipaters of excess energy. Anthocyanins may filter some light at the leaf surface, but they do not participate directly in the energy-dissipation process inside the photosynthetic apparatus.

Carotenoids provide photoprotection by dissipating excess light energy as heat. As accessory pigments in the light-harvesting complexes, they can accept energy that would otherwise overexcite the reaction centers and release it as heat instead of letting it form reactive species. Under high light, the xanthophyll cycle adjusts the pigment composition to boost this non-photochemical quenching, helping to shield photosystems from damage by quenching excited states and preventing the formation of triplet chlorophyll and singlet oxygen. Chlorophyll a and chlorophyll b are the main light absorbers that funnel energy to the reaction centers, not the primary dissipaters of excess energy. Anthocyanins may filter some light at the leaf surface, but they do not participate directly in the energy-dissipation process inside the photosynthetic apparatus.