In their environment, plants are always facing light variations. In order to obtain the best photosynthetic efficiency, or to protect themselves against excess energy, they must acclimate on the short-term and long-term. The Serine/threonine kinase STN7 was already known to be involved in a short-term response (STR) through the mechanism called “state transitions”. Furthermore, studies of recent years provided information suggesting a role of STN7 also in a long-term response (LTR). This work provides highlights on some aspects of the long-term response, which may be triggered by prolonged thylakoid redox imbalance as occurs in mutants of STN7 and PsaL.