Final answer:
Carotenoids are the photosynthesis pigments that serve as antioxidants in plants. They protect plants from oxidative damage by absorbing excess light energy and neutralizing ROS.
Step-by-step explanation:
The photosynthesis pigment that has an important function as an antioxidant is a carotenoid. Carotenoids are a large group of pigments found in various fruits and plants, with well-known types including lycopene, zeaxanthin, and β-carotene. These pigments are embedded within the thylakoid membrane of the chloroplast, where they play a crucial role in photosynthesis by absorbing excess light energy that could otherwise damage the plant and safely dissipating it as heat. Additionally, carotenoids can protect the plant from oxidative stress through their capacity to neutralize reactive oxygen species (ROS), thereby functioning as antioxidants.