The light energy absorbed by the leaves is used for photosynthesis. However, under strong light above the light saturation point, there is a shortage of carbon dioxide relative to the amount of light energy, so not all the absorbed light energy can be used for photosynthesis, resulting in excess light energy (strong light stress). As a result, harmful reactive oxygen species (ROS) are generated, the photosynthetic system is damaged, and photosynthesis is inhibited (photoinhibition) (Fig. 7.1, Taiz and Zeiger 2006).