The Mehler Reaction in Chlamydomonas During Photosynthetic Induction and Steady-State Photosynthesis in Wild-Type and in a Mitochondrial Mutant

Abstract

The Effects Of Fast O2-Removal On Electron Transport Rate (Etr), Measured By Chlorophyll Fluorescence, Were Investigated In Chlamydomonas Reinhardtii. In Wild-Type, O2-Removal Caused A Strong Decrease In Etr During Photosynthetic Induction As A Consequence Of The Absence Of The Mehler Reaction. Light-Saturation Curves Of The O2-Dependent Electron Flow Were Established In Different Conditions. O2-Dependent Electron Flow Was Triggered Within A Few Seconds And Amounted To Up To 80% Of Total Electron Flow During Photosynthetic Induction In Algae Grown On Minimal Medium, While It Represented Less Than 15% At Steady-State. O2-Dependent Electron Flow Was Significantly Weaker In The Presence Of Acetate And In A Mutant Devoid Of Mitochondrial Complexes I And Iii. Measurements Of The Light-Induced Changes Of 820 Nm Transmission In The Seconds Time-Range Show That O2-Dependent Electron Flow Leads To Complete Re-Oxidation Of Psi Donor Side In Wildtype In Saturating Light.