Thylakoid membranes (TM) of the cyanobacterium Synechococcus elongatus were exposed for 30 min to the influence of 0, 10, 100, and 1 000 mM CdCl2 (= Cd0, Cd10, Cd100, and Cd1000). Cd10 and Cd100 caused some increase in activity of photosystem 2, PS2 (H2O → DCPIP), while distinct inhibition was observed with Cd1000. We also observed a similar effect when measuring oxygen evolution (H2O → PBQ + FeCy). Chloroplasts of spinach (Spinacia oleracea L.) were incubated for 30 min with 0, 15, 30, and 60 mM CdCl2 (= Cd0, Cd15, Cd30, and Cd60). All concentrations studied inhibited the PS2 activity, the effect being stronger with increasing concentration of Cd2+. The photosynthetic oxygen evolution activity was also influenced most distinctly by the highest concentration employed, i.e. Cd60. Electrophoretic analysis of the protein composition of cyanobacterium TM showed chief changes in the molecular mass regions of Mr 29 000 and 116 000, while with spinach chloroplasts the most distinct differences were observed in the regions of Mr 15 000 and 50 000. Ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) activity in cyanobacterial spheroplasts still remained on the 40 % level in the case of Cd1000, but it decreased down to approx. 2.5 % in the Cd60 sample of spinach chloroplasts. and M. Nováková, E. Matějová, D. Sofrová.
Photochemical activity of isolated mesophyll chloroplasts was measured as Hill reaction activity (HRA) and photosystem 1 (PS1) activity in three diallel crosses of maize (Zea mays L.) inbred lines and F1 hybrids. Statistically significant differences between genotypes together with positive heterotic effect in F1 generation were found for both traits studied. These differences were more pronounced when HRA or PS1 activity was expressed per leaf area unit or dry matter unit compared to the expression per chlorophyll content unit. Analysis of variance showed that both the genetic and non-genetic components of variation in the photochemical activity of isolated mesophyll chloroplasts are present in all three diallel crosses examined. The positive heterosis in F1 hybrids probably arises from non-additive genetic effects of a positive dominance type. Additive genetic effects were also statistically highly significant. We found no differences between reciprocal crosses. and D. Holá ... [et al.].
The efficiency in selective extraction of photosystem (PS) 2 oxygen evolving complexes was compared among seven detergents. These were applied to thylakoid membranes of the thermophilic cyanobacterium Synechococcus elongatus. Used were five non-ionic detergents with one ionic and one zwitterionic for comparison. To compare the suitability and efficiency of the detergents the following properties of the extracts were examined: maximum rate of oxygen evolution with various electron acceptors, the relative variable fluorescence (FV/FM), the contamination of the extract with photosystem (PS) 1, and the status of the electron acceptor side of PS2 reaction centre. None of the detergents yielded a highly selective extraction of the PS2 complexes (negligible contamination with PS1) which would simultaneously display a high photochemical activity and high structural intactness. Heptylthioglucoside and dodecylmaltoside yielded the nearest approximation to the optimum result. Kinetic fluorometry was applied here for the first time to characterize the functional and structural properties of PS2 particles from cyanobacteria. and E. Šetlíková ... [et al.].
Pigment-protein complexes enriched in photosystem 1 (PS1) and, for comparison, enriched in photosystem 2 (PS2) were isolated from the cyanobacterium Synechococcus elongatus Nag. f. thermalis Geitl. They were immobilized and oriented in the polyvinyl alcohol (PVA) films, and studied by linear dichroism (LD), fluorescence polarization (FP), photoacoustic spectroscopy (PAS), and polarized photoacoustic spectroscopy (PAS|| and PAS⊥). The LD signal of β-carotene in the region with maximum at 500 nm was positive in the PS1 complex. The maximum value of fluorescence polarization (FP) in the measured photosynthetic pigment region was 1.25 and was similar to higher plant values. Carotenoids exhibited different efficiencies of thermal deactivation (max. at 500 nm) in PS1 and PS2. The thermal deactivation efficiency of carotenoids in comparison with that of chlorophyll (Chl) a at its red absorbance maximum was much higher in PS1 than in PS2 complexes. Cyanobacterial complexes did not contain Chl b, interpretation of the LD, PAS, and FP results is thus easier and can be compared with PS1 and PS2 values of higher plants, especially with Chl b-less mutant values. and G. E. Białek-Bylka ... [et al.].
Intact cells of Synechococcus elongatus were treated with different concentrations (0.1 and 1.0 mM = Cd0.1, Cd1.0) of CdCl2 for 24 h. Cd0.1 treatment stimulated growth of the cell culture and chlorophyll (Chl) a concentration in the culture. Cd1.0 inhibited both the above mentioned parameters. The oxygen evolving activity of intact cells (H2O → BQ) as well as of isolated thylakoid membranes, TM (H2O → DCPIP; H2O → PBQ + FeCy) decreased after 24 h of Cd1.0 cultivation to 7 %. Photosystem 1 (PS1) activity was less sensitive to the effect of Cd2+ than PS2 activity. CdCl2 concentration in cultivation media after 24 h of cultivation proved that the cyanobacterium cells take up these ions to a large extent from the cultivation medium. After 24 h of the Cd1.0 treatment only 12 % of the amount of Cd2+ originally added to the cultivation medium was found. The ratio of external-antenna pigments, phycocyanin, and allophycocyanin to Chl increased approximately twofold with growing Cd2+ concentration in the cultivation medium. This ratio was found in both TM and dodecylmaltoside extracts. and E. Tůmová, D. Sofrová.