Non Photochemical Quenching mechanism in higher plants and in the unicellular alga Chlamydomonas reinhardtii

Light is a necessary ecological factor for oxygenic photoautotrophic organisms. Plants and algae require light for life but it can sometimes become a limiting factor or even cause stress events. Among the different mechanisms evolved to cope with excessive light, the Non Photochemical Quenching (NPQ) seems to be the most efficient process in both plants and algae. The NPQ value can be attributed to three different components (qE, qT and qI). A central problem for eco †" physiology is the quantification of the partitioning of the excitation energy into the different mechanisms. To investigate the variability in the extent of the three components on external parameters, different experiment were performed. My research showed that utilizing inhibitors or mutants lines of Arabidopsis a variation in the components was inducted. The analysis of the fluorescence parameters were further developed and in this work a revised energy partition approach will be proposed. Moreover, seen that it is very important avoid light stress situation this research proposed the NMR (Nuclear Magnetic Resonance) as a useful tool in the detection of stress situation in vegetal extracts. In regard to Chamydomonas reinhardtii not so many information are collected on the NPQ. Interestingly, analyses of a suppressor of the npq4 mutation seemed to partly restore the wild-type NPQ value. This suggests a role not only for protein LHCS3 , but also for LHCSR1.