The flash-induced electrochromic absorbance change (ΔA515) was measured in leaves of higher plants in the absence and presence of continuous monochromatic background illumination of different intensities and wavelengths. The variation of the amplitude of ΔA515 in background light was used to estimate the steady-state turnover time of the electron transport. In red light we obtained about 5 msec which was accounted for by the turnover of the linear electron transport. With far red background illumination or in the presence of the photosystem 2 inhibitor, DCMU, the steady-state turnover time tentatively assigned to photosystem 1 cyclic electron transport was much larger (≥100 msec). Increasing the intensity of background illumination with far red light gradually diminished the slow rise of ΔA515 in parallel with suppression of the initial rise generated by photosystem 1. At high intensities of the red light, however, while ΔA515 was attenuated, the slow rise was not eliminated and its proportion relative to the initial rise did not vary appreciably.
- slow rise of ΔA
- turnover rate of electron transport
ASJC Scopus subject areas
- Cell Biology