The xanthophyll cycle

Abstract

Among all the carotenoids which are present in the photosynthetic membranes of higher plants, only three undergo rapid, light-induced changes in their concentration. These are the three xanthophylls of the xanthophyll cycle and they undergo intercon versions induced by changes in light intensity. Furthermore, the acclimation of photosynthetic organs to high light involves a strong increase in the total sum of these three xanthophylls. Both the interconversions among the components of the xanthophyll cycle and the increase of the size of the total xanthophyll cycle pool occur in response to light stress. Plants are subjected to light stress in the field in high light habitats, as well as in habitats where they encounter other environmental stress factors in combination with light. The characteristics of the xanthophyll cycle are discussed here in relation to its specific association with high light stress and its recently described function in a photoprotective process of fundamental importance.