PROTECTION OF PHOTOSYSTEM II (PSII) BY NATURAL ANTIOXIDANTS FROM HEAVY METALS - INDUCED STRESS
Keywords:
Ceratostigma plumbaginoides bunge, antioxidants, delayed chlorophyll fluorescence, Zn2+, Ni2+Abstract
The comparative analysis of protective properties of biologically active composition (BAC) on
the base of plumbagin (2-methyl, 5-hydroxi, 1.4-naphthoquinone) and Na-ascorbate (Na-asc) under
toxic action of Zn2+ and Ni2+ on photosystem II (PSII) was carried out. The investigations were performed
on wheat seedlings (Triticum aestivum L.) by means of introduction of metal ions and protective
substances by two ways: simultaneously and consecutive incubations of wheat seedlings. The action of metal ions and defense effectiveness were evaluated by means of analysis of induction curves of delayed fluorescence of chlorophyll a in millisecond range (msec-DF of Chla) in wheat seedlings. The character of induction transitions changes of msec-DF of Chla under action of heavy metals was found to be indicated on suppression of radical pair primary charge separation and electron flow rate
to primary quinone acceptor QA on donor side of PSII. BAC (at less degree) and Na-asc decreased toxic action of Zn2+ and Ni2+ that is likely to be due to neutralization of formed superoxide anion radicals, and thus restoration of oxidation-reduction equilibrium between photosystems
