REVIEW Uptake of diuron and concomitant loss of photosynthetic activity in leaves as visualized by imaging the red chlorophyll fluorescence Hartmut K. Lichtenthaler • Gabriele Langsdorf • Claus Buschmann Received: 28 January 2013 / Accepted: 26 April 2013 / Published online: 31 May 2013 Ó Springer Science+Business Media Dordrecht 2013 Abstract The principles of the chlorophyll (Chl) fluo- rescence induction kinetics (known as Kautsky effect) and their change by the photosystem II herbicide diuron are presented together with the Chl fluorescence emission spectra of a normal and diuron-inhibited leaf. By imaging the Chl fluorescence emission of green leaves the succes- sive uptake of diuron and the concomitant loss of photo- synthetic quantum conversion from the leaf base to the leaf tip are documented. Keywords Chlorophyll fluorescence decrease ratio R Fd Á Digitalis purpurea Á Herbicide action Á Phaseolus vulgaris Á Photosystem II herbicide Abbreviations Chl Chlorophyll F690/F740 Ratio of the two peaks of chlorophyll fluorescence emission spectra Fd Chl fluorescence decrease FL-FIS Flash-lamp fluorescence imaging system Fm and Fs Maximum and steady-state Chl fluorescence R Fd Variable Chl fluorescence decrease ratio Introduction The light-induced red chlorophyll (Chl) fluorescence of green leaves and its relationship with the photosynthesis activity of leaves has first been demonstrated and studied by Kautsky in the 1930s (Kautsky and Hirsch 1931) as reviewed in detail by Lichtenthaler (1992) and Govindjee (1995). The Chl fluorescence induction kinetics consist of two components (a) a fast rise of the Chl fluorescence within seconds to a maximum Fm and (b) a slow decline to a considerably lower steady-state value Fs within 4–6 min after the onset of illumination. The fast Chl fluorescence rise and the slow fluorescence decrease kinetics have become an essential signature of photosynthesis. From these induction kinetics several Chl fluorescence parame- ters and ratios (e.g., Fv/Fm and R Fd ) have been established to judge the functionality of the photosynthetic apparatus (Butler and Kitajima 1975; Schreiber et al. 1986; Lich- tenthaler 1988; Lichtenthaler and Rinderle 1988; Govind- jee 1995; Papageorgiou and Govindjee 2004). The Chl fluorescence kinetics proceed faster in leaves with higher photosynthetic rates, e.g., in sun plants as compared to shade plants (Fork and Govindjee 1980). In addition, it was shown by Lichtenthaler et al. (1981) that the Chl fluores- cence decrease (Fd) from the maximum Fm to the steady- state fluorescence (Fs) is considerably higher in sun and high-light leaves which contain higher photosynthetic rates as compared to shade and low-light leaves. In fact, the values of the Chl fluorescence decrease ratio R Fd (= Fd/Fs) reflect the different rates of net photosynthetic CO 2 fixation of leaves (Lichtenthaler et al. 1981) and the R Fd values are linearly correlated to the net photosynthesis rates P N of sun and shade leaves (Lichtenthaler and Babani 2004; Lich- tenthaler et al. 2007a; b; Sarijeva et al. 2007). Photosystem II herbicides, such as diuron (DCMU (3- (3 0 ,4 0 -dichlorophenyl)-1,1-dimethylurea) block the photo- synthetic quantum conversion (Wessels and van der Veen 1956; Pfister et al. 1974) by binding to the D1, the Q B - binding reaction center protein of photosystem II (Astier Guest Editor: Gerald Edwards. Dedicated to Prof. Govindjee on the occasion of his 80th birthday. H. K. Lichtenthaler (&) Á G. Langsdorf Á C. Buschmann Botanisches Institut (Physiology and Biochemistry of Plants), Karlsruhe Institute of Technology (KIT), University Division, Kaiserstr. 12, 76128 Karlsruhe, Germany e-mail: hartmut.lichtenthaler@kit.edu 123 Photosynth Res (2013) 116:355–361 DOI 10.1007/s11120-013-9842-1