High Temperature Induced Alterations in the Photosynthetic Electron Transport Activities of the Spheroplasts of Synechococcus 6301

Photosystem II and whole chain electron transport activities of spheroplasts isolated from Synechococcus declined due to high temperature treatment beyond 35°C. Unlike PSII, the Photosystem I activity showed enhancement due to high temperature treatment. The intersystem catalyzed PSI electron transport was extremely sensitive to high temperature indicating the plastoquinone as main target. Light intensity measurements of PSII catalyzed electron transport clearly indicated that alterations in the light-harvesting complex II (phycobilisomes) is responsible for the altered PSII photochemistry in this cyanobacteria.