Fluorescence kinetic parameters and cyclic electron transport in guard cell chloroplasts of chlorophyll-deficient leaf tissues from variegated weeping fig (<Emphasis Type="Italic">Ficus benjamina</Emphasis> L.) |
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Authors: | Vladimir Lysenko |
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Institution: | (1) Scientific Research Institute of Biology, Southern Federal University, Stachky Ave 194/1, 344090 Rostov-on-Don, Russia |
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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 Rfd740/Rfd690 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 CO2-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. |
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