Abstract
Plants have a energy dissipating mechanism called qE-quenching (qE) induced by pH of trans-thylakoid membranes under excess light conditions. It has been suggested that zeaxanthin formed by de-epoxidation of violaxanthin (xanthopyll cycle) is involved in qE in higher plants. However, Chamydomonas reinhardtii has a decreased level of qE and does not express PsbS protein that is essential for qE in higher plants. Therefore, it is inferred that the mechanism of qE could differ among plant species. In this study, we performed PAM fluorescence measurement and HPLC analysis using a mutant npq1 lor1 that lacks violaxanthin de-epoxidase and does not accumulate zeaxanthin. The results indicated that npq1 lor1 and wild type showed similar levels of qE. Therefore, it is suggested that the small level of qE obserbed in Chlamydomonas is independent of xanthophyll cycle.
