Chlorophyll fluorescence as an indicator of heat induced limitation of photosynthesis in Arbutus unedo L.

Abstract

Chlorophyll fluorescence analysis may provide us with a sensitive indicator of stress induced limitations of photosynthesis (for recent reviews see Smillie and Hetherington (1983) and Schreiber and Bilger, this volume). High temperature treatment causes a variety of fluorescence changes: (1) At elevated temperatures the dark fluorescence level, Fo, is increased several-fold (Schreiber and Berry 1977), the critical temperature for the Fo-increase being closely correlated with the critical temperature for irreversible damage to the leaf tissue as determined from leaf necrosis (Bilger, Schreiber and Lange 1984). (2) Following heat treatment, there is a decrease in variable fluorescence, Fvar, as measured upon illumination at room temperature (Krause and Santarius 1975; Santarius and Muller 1979). In isolated chloroplasts this decrease in variable fluorescence has been correlated with damage to the watersplitting system (Yamashita and Butler 1968). (3) Mild heat treatment, which does not cause irreversible tissue damage, induces changes in the low temperature fluorescence emission spectra indicative of a heat induced state I – state II shift, i.e. of a change in energy distribution in favor of photosystem I (Weis 1984,1985).