Photoinhibition

Under photoinhibition refers to the inhibition of photosynthesis by high light levels far above the light saturation point.

The causes of photoinhibition, are the energy oversaturation of the pigment system. Proportion is in the reaction center of photosystem II

Absorbed light energy is converted into heat more there, and it comes to the reduction of the photoelectron transport. If this excess excitation energy from PS II can not be delivered, the excited chlorophyll ( attained energy level of the π - electrons of chlorophyll = by heat emission and electron spin reversal) is preferably in the triplet state so highly reactive singlet oxygen is formed.

If these two conditions can not be intercepted by the β -carotene or xanthophyll (conversion of the excess excitation energy to heat ), it comes to photo-oxidation of chlorophyll and thus its inactivation.

Particularly apparent photoinhibition shows in plants with C3 photosynthesis in arid and subtropical areas ( for example, all kinds of fruit ). These plants with their low potential photosynthesis, which is already saturated with a low light irradiation are particularly susceptible to photoinhibition.

C4 plants with a high photosynthetic potential, which is saturated at relatively high light availability, on the other hand tolerate a much higher light.

• Photosynthesis