Concurrent Monitoring of Oxygen Evolution and Chlorophyll Fluorescence in Peeled Leaves with a Liquid-phase Oxygen Electrode

Abstract

Concurrent monitoring of photosynthetic rate and chlorophyll fluorescence is one of the useful methods to understand the chemical energy balance in photosynthesis. The liquid-phase oxygen electrode is widely employed for determining photosynthetic rate by monitoring oxygen evolution from leaf segments in reaction solution. If it is possible to measure the emittance of chlorophyll fluorescence concurrently with oxygen evolution rate in leaf by the oxygen electrode method, it may become a valid technique for studying the energy flow in photosynthesis of leaf in various physical and chemical solution conditions. We set up a system for concurrent measurement of gross oxygen evolution rate (Og) and chlorophyll fluorescence by partially remodeling a conventional type of liquid-phase oxygen electrode. A piece of 0.785 cm2 leaf with the abaxial epidermis peeled off was fixed in solution of the electrode, and Og and quantum yield of PSII (Fe) were concurrently measured. By the addition of ATP to solution Fe was temporarily decreased, whereas Og was unchanged. Change in osmotic potential from ¿0.3MPa to ¿1.5 MPa did not affected Og in a leaf, but Fe was gradually reduced with a decrease in the osmotic potential of solution. It may be expected that the concurrent measurement by this remodeled electrode is widely used for analysis of energy balance in photosynthesis and energy utilization efficiency in crop leaves.