ABSTRACT
This chapter focuses on the xanthophyll cycle pigments of green leaves. Exposure of plants to intense light can result in the formation of destructive activated oxygen species within the photosynthetic apparatus of leaves. Chlorophyll and the utilization of light is photosynthetic carbon metabolism. The formation and removal of zeaxanthin, that is the turnover of the xanthophyll cycle, is observed under natural conditions during the course of the day in sun-exposed habitats. When excitation energy is dissipated thermally in the photochemical system; the operation of this process results in a decrease in the efficiency of photosynthetic energy conversion. The xanthophyll cycle provides a means of rapidly interconverting the xanthophylls of the cycle, in response to changes in the balance between the absorption of light by chlorophyll and the utilization of light through photosynthetic carbon metabolism. Exposure of plants to various environmental stress factors almost inevitably leads to a decrease in the rate of photosynthesis.
