Differences in stress defence mechanisms in germinating seeds of Pinus sylvestris exposed to various lead chemical forms.

Exposure to lead (Pb) can have serious toxic effects on the physiological and biochemical processes of plants. The chemical form of the metal determines the degree of its toxicity. In our research, we examined the effect of lead in the form of lead nitrate [Pb(NO3)2] and lead chloride (PbCl2) in concentrations of 12.5 mM and 25 mM on pine (Pinus sylvestris) seed germination. Nitrogen salt causes more severe changes than chloride salt. Increasing levels of electrolyte leakage, malondialdehyde, and hydrogen peroxide were detected during germination processes. The high levels of ROS lead to redox changes in the cell. We observed a reduction in the level of the reduced form of glutathione (GSH), and at the same time observed increased levels of the oxidised form of glutathione (GSSG) depending on the concentration and also the time of exposure to lead compounds. At the beginning of germination processes, the effective non-enzymatic activity of the antioxidant cycle was dominant, and at the late stage the enzymatic activity was noticed in the presence of Pb compounds. CAT activity significantly increased after Pb compound exposition.