Temperature-dependent changes in Photosystem II heterogeneity support a cycle of Photosystem II during photoinhibition

✍ Scribed by Esa Tyystjärvi; Eva-Mari Aro

• Publisher: Springer
• Year: 1990
• Tongue: English
• Weight: 717 KB
• Volume: 26
• Category: Article
• ISSN: 0166-8595
• DOI: 10.1007/bf00047082

✦ Synopsis

High light treatments were given to attached leaves of pumpkin (Cucurbita pepo L.) at room temperature and at I°C where the diffusion-and enzyme-dependent repair processes of Photosystem II are at a minimum. After treatments, electron transfer activities and fluorescence induction were measured from thylakoids isolated from the treated leaves. When the photoinhibition treatment was given at I°C, the Photosystem II electron transfer assays that were designed to require electron transfer to the plastoquinone pool showed greater inhibition than electron transfer from HzO to paraphenylbenzoquinone, which measures all PS II centers. When the light treatment was given at room temperature, electron transfer from H20 to paraphenyl-benzoquinone was inhibited more than whole-chain electron transfer. Variable fluorescence measured in the presence of ferricyanide decreased only during room-temperature treatments. These results suggest that reaction centers of one pool of Photosystem II, non-QB-PS II, replace photoinhibited reaction centers at room temperature, while no replacement occurs at I°C. A simulation of photoinhibition at I°C supports this conclusion.