Cadmium is one of the most dangerous environmental pollutants, affecting, among other things, plant mineral composition. It easily interacts with iron, one of the most important elements for plant growth and metabolism. This interaction, including modifying effects of lowered or excessive Fe supply on Cd-exposed plants and its consequences for the photosynthetic apparatus is reviewed. The influence of modified Fe and Cd supply on the uptake of both metals, their distribution, plant growth, and photosynthesis is also explained. Moderate Fe excess has a beneficial influence on Cd-treated plants, resulting in more intensive growth, photosynthetic pigments accumulation, and more efficient light phase of photosynthesis. Nutrient-medium Fe deficiency increases plant susceptibility to Cd. The main open questions of Cd/Fe interaction are: (1) the strong Fe-dependency of Cd mobility within the plant, and (2) photosynthetic dark phase adaptation to Cd stress. and A. Siedlecka, Z. Krupa.
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.