what is meant by photo-oxidation.How does accessory pigments protect chlorophyll a from photo oxidation?

Photo-oxidation is the process of oxidation induced by light. It is a deleterious process as it results in the generation of free radical ions, or reactive oxygen species having single valence electron. These molecules are harmful for the proteins and cellular components as they oxidize and denature them.

In plants, accessory pigments like zeaxanthin, a carotenoid belonging to the group of xanthophylls and chlorophyll b protects the chlorophyll a from photo-oxidation.