Too much of a good thing: light can be bad for photosynthesis.
Even though light is the ultimate substrate for photosynthetic energy conversion, it can also harm plants. This toxicity is targeted to the water-splitting photosystem II and leads to damage and degradation of the reaction centre D1-polypeptide. The degradation of this very important protein appears to be a direct consequence of photosystem II chemistry involving highly oxidizing radicals and toxic oxygen species. The frequency of this damage is relatively low under normal conditions but becomes a significant problem for the plant with increasing light intensity, especially when combined with other environmental stress factors. However, the plant survives this photoinhibition through an efficient repair system which involves an autoproteolytic activity of the photosystem II complex, D1-polypeptide synthesis and reassembly of active complexes.
Barber
J
J
Wolfson Laboratories, Biochemistry Department, Imperial College of Science, Technology and Medicine, London, UK.
Andersson
B
B
D000595:Amino Acid Sequence; D008027:Light / Q000009:adverse effects*; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010788:Photosynthesis / Q000528:radiation effects*; D045322:Photosynthetic Reaction Center Complex Proteins / Q000528:radiation effects; D045332:Photosystem II Protein Complex; D010940:Plant Proteins / Q000378:metabolism
D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D010940:Plant Proteins