2001). During the past BMN 673 supplier 10 years the KLAS has been further developed for measurements in the near-infrared and to support deconvolution of P700 and plastocyanin absorbance changes. Furthermore, in the 505–570 nm wavelength range now eight dual-wavelengths difference signals are measured quasi-simultaneously instead of 16 single beam signals, with the advantage that non-specific optical disturbances and signal changes are more effectively suppressed in the difference mode (Klughammer and Schreiber, in preparation). For measurements of rapid ECS (P515) changes, only one
of the eight dual-wavelengths channels can be used, with a corresponding increase of time resolution (now 30 μs). The commercially available Dual-PAM-100, with which the measurements of the present study were carried out, is equivalent to a one channel dual-wavelength KLAS combined with a PAM fluorometer. While the basic version of this device measures the 870–820 nm dual-wavelength difference signal (P700), we have developed an accessory emitter–detector module optimized for measuring the 550–520 nm dual-wavelength difference signal (ECS and P515) simultaneously with the single beam 535 nm signal (“light scattering”) instead of Chl fluorescence
(Schreiber and Klughammer 2008). Here we will concentrate on the ECS (P515) signal and on the charge-flux information carried by this signal upon rapid modulation of the actinic light. Our study builds on extensive previous work by Joliot, SN-38 research buy Kramer and co-workers on dark-interval relaxation kinetics (DIRK) of P515 (ECS), which not only contain information
on the pmf and its partitioning into its ΔpH and ΔΨ components (Sacksteder and Kramer 2000; Cruz et al. 2001), but also on the light-driven charge flux (Joliot and Joliot 2002; Kramer et al. 2004a, b; Joliot and Joliot 2006; Takizawa et al. 2007; Livingston et al. 2010). We will report on a special “flux mode” of Dual-PAM-100 operation, involving 1:1 light:dark modulation of AL on top of pulse amplitude GPX6 modulation of the two ML beams. It will be shown that the “P515 flux” signal provides a reliable continuous measure of light-driven charge fluxes in photosynthesis, correlating well with simultaneously measured CO2 uptake in intact leaves. Deviations between the two signals can be interpreted in terms of alternative types of electron flow, regulatory changes in the conductivity of the reversible ATP synthase or of the H+/e − ratio (see Kramer et al. 2004a, b for a reviews). Materials and methods Experimental setup for simultaneous measurements of P515 and CO2 uptake Experiments involving simultaneous measurements of P515 and CO2 uptake (Figs. 8, 9, 10) were carried out under controlled conditions of gas composition and temperature. A Dual-PAM-100 measuring system was combined with a GFS-3000 gas exchange measuring system.