ESTIMATION OF NONCYCLIC ELECTRON-TRANSPORT IN-VIVO OF TRITICUM USING CHLOROPHYLL FLUORESCENCE AND MASS-SPECTROMETRIC O-2 EVOLUTION

A mass spectrometric O-16(2)/O-18(2) technique was used to determine t he rate of gross O-2 evolution in attached leaves of Triticum aestivum under several environmental conditions. Simultaneously, fluorescence emission was determined from the upper and the lower sides of the leaf . The rate of non-cyclic electron now derived from gross O-2 evolution deviated from the rates predicted from fluorescence measurements. Thi s deviation varies depending on environmental conditions and on the si de on which the leaf fluorescence is being measured. Our data clearly indicate that fluorescence measurements provide trends in electron tra nsport but do not yield accurate electron transport rates of the entir e leaf.