Concurrent Monitoring of Oxygen Evolution and Chlorophyll Fluorescence in Mungbean Leaves with a Liquid-Phase Oxygen Electrode

In the liquid-phase oxygen electrode, photosynthetic rate is determined by the rate of oxygen evolution from sliced leaf pieces stirred in CO2-saturated reaction solution. The slicing and stirring treatments promote CO2 absorption of leaf pieces, but there is some difficulty in determining fluorescence emittance from the moving objectives. The barrier of CO2 uptake into leaf was removed by peeling its epidermis, and oxygen evolution rates from peeled leaves were readily measured (Yatomi, M. et al. 1992). A liquid-phase oxygen electrode was partly improved to make concurrent measurements of oxygen evolution rate and chlorophyll fluorescence quenching. In this study, we used this tool and observe the responses of gross oxygen evolution rate (Og), the quantum yield of PSII ( e) and photorespiration rate (Pr) to the changes of photosynthetic environment.