Comparison of new continuous flux approach with point-by-point DIRK approach The potential of the point-by-point DIRKECS approach for obtaining in vivo information on the dynamic flexibility of photosynthetic charge fluxes has been demonstrated

in numerous previous studies (Kramer and Sacksteder 1998; Cruz et al. 2001; Sacksteder et al. 2001; Joliot and Joliot 2002; Joliot et al. MAPK inhibitor 2004; Avenson et al. 2004a). Therefore, for the acceptance of the new continuous flux approach it is important to show that the obtained information is equivalent to that provided by the proven DIRKECS method. Comparative measurements with both 8-Bromo-cAMP order methods were carried out using the same leaf under close to identical conditions. For this purpose, the leaf was repetitively illuminated every 30 s for 10 s at 1,920 μmol m−2 s−1. When after 50 illumination cycles the kinetic response was constant, three DIRKECS data sets were recorded at times 0.2, 5.0, and 9.5 s after onset of actinic illumination, by measuring the fast decay kinetics during a 40 ms dark-period. Each data set consisted of 50 averages, all measured under the same repetitive regime of illumination. Figure 7a shows the resulting three decay curves with indication of the initial slopes, which were determined by linear regression using the data points of the first 2 ms after light-off only. Fig. 7 click here Comparison of continuous charge flux method with point-by-point

DIRKECS method. a Determination of initial slopes of the ECS (P515) relaxation during 40 ms dark

intervals for three points in the time course of repetitively measured dark-light induction curves (30 s repetition cycle) of a dandelion leaf. Average of 50 recordings. AL intensity, 1,920 μmol m−2 s−1. b Dark-light induction curve of continuous charge flux signal (bottom) measured with the same leaf under close to identical conditions as in a. Black points rate of charge flux determined from initial Cepharanthine slopes in a for comparison. P515 signal measured in the flux mode (top). Averages of 50 recordings. AL was 1:1 light:dark modulated with 2 ms on/off periods. Damping 10 μs. Average intensity, 1,920 μmol m−2 s−1. For further explanations, see text After having recorded the three DIRKECS data sets, the system was switched to flux mode and the actinic intensity was doubled, so that the average light intensity during 1:1 modulation again was 1,920 μmol m−2 s−1. Then the same repetitive regime of illumination was established and 50 illumination cycles were averaged in the flux mode with 2 ms on/off periods. Figure 7b shows the resulting charge flux induction curve (bottom) and also the simultaneously measured induction curve of the original P515 signal (top). The three black dots on top of the charge flux curve correspond to the initial slope data shown in Fig. 7a. Charge flux originally measured in units of ΔI/(I × Δt) s−1 (i.e.