Fluorescence kinetic parameters and cyclic electron transport in guard cell chloroplasts of chlorophyll-deficient leaf tissues from variegated weeping fig (Ficus benjamina L.)

Abstract

Residual chlorophyll in chlorophyll-deficient (albino) areas of variegated leaves of Ficus benjamina originates from guard cell chloroplasts. Photosynthetic features of green and albino sectors of F. benjamina were studied by imaging the distribution of the fluorescence decrease ratio Rfd within a leaf calculated from maximum (Fm) and steady-state leaf chlorophyll fluorescence (Fs) at 690 and 740 nm. Local areas of albino sectors demonstrated an abnormally high Rfd(740)/Rfd(690) ratio. Fluorescence transients excited in albino sectors at red (640 and 690 nm) wavelengths showed an abrupt decrease of the Rfd values (0.4 and 0.1, correspondingly) as compared with those excited at blue wavelengths (1.7-2.4). This "Red Drop" was not observed for green sectors. Normal and chlorophyll-deficient leaf sectors of F. benjamina were also tested for linear and cyclic electron transport in thylakoids. The tests have been performed studying fluorescence at a steady-state phase with CO(2)-excess impulse feeding, photoacoustic signal generated by pulse light source at wavelengths selectively exciting PSI, fluorescence kinetics under anaerobiosis and fluorescence changes observed by dual-wavelength excitation method. The data obtained for albino sectors strongly suggest the possibility of a cyclic electron transport simultaneously occurring in guard cell thylakoids around photosystems I and II under blue light, whereas linear electron transport is absent or insufficient.

Far-Red Spectrum of Second Emerson Effect: A Study Using Dual-Wavelength Pulse Amplitude Modulation Fluorometry

“…Thus we showed that only a Cyclic Electron Transport (CET-PSII or/and CET-PSI) occurs in the stomata cells thylakoids of albino leaf sectors of variegated Ficus benjamina plants under excitation by blue light whereas a non-cyclic electron transport is absent. Such a conclusion was based, among other facts, on the absence of any changes of chlorophyll fluorescence excited at 470 nm in response to the applying of the supplementary far-red light (Lysenko, 2012). In contrast, normal green tissues possessing a non-cyclic electron transport, show a clear increase of photochemical fluorescence quenching in this case, that was first discovered by Govindjee and Rabinowitch (1960) and confirmed in our work (Lysenko, 2012).…”

“…Besides, far-red light can be used in dualwavelength excitation experiments to test PSI and PSII coupling within a single linear electron transport chain (Lysenko, 2012). Thus we showed that only a Cyclic Electron Transport (CET-PSII or/and CET-PSI) occurs in the stomata cells thylakoids of albino leaf sectors of variegated Ficus benjamina plants under excitation by blue light whereas a non-cyclic electron transport is absent.…”

“…PAM-fluorometry was used in our modification based on a real-time, fast-Fourier spectrometry to select the measured signal, instead of traditional usage of lock-in amplifier. An analogous modification was previously being applied to process the photoacoustic signals, that allows to use of extremely low measuring light at an acceptable level of signal-to-noise ratio (Matishov et al, 2010;Lysenko, 2012;Lysenko and Varduny, 2013). Besides saturating flashes, we also used far-red light pulses of moderate intensity to assess the resulting changes in the amplitude of the signal from F 0 to the lower values (Fs).…”

“…Such a conclusion was based, among other facts, on the absence of any changes of chlorophyll fluorescence excited at 470 nm in response to the applying of the supplementary far-red light (Lysenko, 2012). In contrast, normal green tissues possessing a non-cyclic electron transport, show a clear increase of photochemical fluorescence quenching in this case, that was first discovered by Govindjee and Rabinowitch (1960) and confirmed in our work (Lysenko, 2012). The general assumption here is that the illumination of leaves with a far-red light drives PSI, which is coupled with PSII in a single electron transport chain and as a result, facilitates electron sink from PSII, that increases quantum yield of PSII and consequently increases photochemical fluorescence quenching (Govindjee and Rabinowitch, 1960;Lysenko, 2012).…”

Anthocyanin-dependent anoxygenic photosynthesis in coloured flower petals?

“…In our preliminary studies with P. hybrida flower petals, such a “short pulse” technique produced a sufficiently higher ES (8–10%) compared to that of the commonly used “long pulse” method (ES < 2%); this result is most likely due to the high instantaneous light intensity of the pulse, adapting the proposed ADAPFP to be more efficient. It should be noted here that the “short pulse” technique can be applied only when the PA signal is processed using fast Fourier transform instead of the commonly used lock-in amplifier as described in our previous work14.…”