CHLOROPHYLL FLUORESCENCE DECAY PROFILES OF O3-EXPOSED SPRUCE NEEDLES AS MEASURED BY TIME-CORRELATED SINGLE PHOTON-COUNTING

Chlorophyll fluorescence decay profiles have been measured in the wavelength range 680-720 nm for needles from Norway spruce [Picea abies (L.) Karst] trees which have been exposed to ozone. All profiles required three exponential components of lifetime 100-150 ps, 400-600 ps and 3.5-5.0 ns to fit the experimental data. Compared to control samples, the ozone-treated needles exhibited a greater amount of the longest-lived chlorophyll fluorescence and a redistribution in intensity for both the other components from 720+ to 690 nm. These observations are interpreted in terms of disruption of energy transfer and break-up of light-harvesting complexes on exposure to ozone. The potential for use of the technique in monitoring forest decline is discussed.