A cyclic series of interconversions involving certain xanthophylls, which plays a vital role in the photoprotection of plant chloroplasts. Under intense illumination, violaxanthin is converted, via an intermediate, to zeaxanthin. The latter is thought to receive excess energy from chlorophyll and dissipate this as heat, thereby avoiding possible damage to the photosynthetic apparatus. In dim light, the zeaxanthin is reconverted to violaxanthin, so that all incident light energy is used for photosynthesis.
Subjects: Biological Sciences.