Calcium protection of PS2 complex of Phaseolus coccineus from cadmium toxicity: In vitro study

The action of 10 and 20 mM Ca against harmful Cd effect on PS2 complex isolated from leaves of Phaseolus coccineus L. cv. Piękny Jaś was studied. The changes in fast chlorophyll a fluorescence induction kinetics and protein composition of PS2 complex were the symptoms of Cd toxicity and Ca protection of PS2 complex. Calcium applied at 10 mM concentration prevented F0 reduction caused by the presence of 250-1000 μM Cd in the incubation mixture, but that of (the variable chlorophyll a fluorescence) Fv, Fm, Fv/F0, and Fv/Fm only at 250 μM Cd. Ca concentration doubling in the incubation mixture resulted in complete overcoming the toxicity of 250-1000 μM Cd to Fv and Fm. However, the protection of Fv/F0 and the photochemical efficiency of PS2 (Fv/Fm) from 1000 μM Cd was only partial even at 20 mM Ca. A protective effect of 10 mM Ca on D1, D2 and 17 kDa proteins was found in PS2 complex exposed to 250 μM Cd, and on 43 kDa protein in the complex treated with 500 μM Cd. However, 20 mM Ca counteracted the toxicity of 500 μM Cd to the 43, 47 and 17 kDa proteins, as well as the harmful effect of 1000 μM Cd on 47 and 17 kDa ones.