TY  - JOUR
A1  - Klughammer, Christof
A1  - Siebke, Katharina
A1  - Schreiber, Ulrich
T1  - Continuous ECS-indicated recording of the proton-motive charge flux in leaves
JF  - Photosynthesis Research
N2  - Technical features and examples of application of a special emitter–detector module for highly sensitive measurements of the electrochromic pigment absorbance shift (ECS) via dual-wavelength (550–520 nm) transmittance changes (P515) are described. This device, which has been introduced as an accessory of the standard, commercially available Dual-PAM-100 measuring system, not only allows steady-state assessment of the proton motive force (pmf) and its partitioning into ΔpH and ΔΨ components, but also continuous recording of the overall charge flux driven by photosynthetic light reactions. The new approach employs a double-modulation technique to derive a continuous signal from the light/dark modulation amplitude of the P515 signal. This new, continuously measured signal primarily reflects the rate of proton efflux via the ATP synthase, which under quasi-stationary conditions corresponds to the overall rate of proton influx driven by coupled electron transport. Simultaneous measurements of charge flux and \(CO_2\) uptake as a function of light intensity indicated a close to linear relationship in the light-limited range. A linear relationship between these two signals was also found for different internal \(CO_2\) concentrations, except for very low \(CO_2\), where the rate of charge flux distinctly exceeded the rate of CO2 uptake. Parallel oscillations in \(CO_2\) uptake and charge flux were induced by high \(CO_2\) and \(O_2\). The new device may contribute to the elucidation of complex regulatory mechanisms in intact leaves.
KW  - photosynthetic electron transport
KW  - P515
KW  - DIRK method
KW  - CO2 gas exchange
KW  - Dual-PAM-100
KW  - electrochromic absorbance shift
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-132134
VL  - 117
ER  -