The effect of cadmium-nickel interactions on superoxide production, cell viability and membrane potential (EM) in roots of two maize cultivars.

Effects of CdCl2, NiCl2 or both on superoxide production, viability and membrane potential (EM) of root cells in meristematic (MZ) and differentiation (DZ) zones of two maize cultivars (cv. Premia and cv. Blitz) were studied. Plants were supplied with 10 and 100 μM concentrations of heavy metals (HM). The responses in the studied parameters to HM were concentration- and time-dependent, and were found only in the cells of MZ. The treatment of roots with Cd-stimulated massive superoxide production, although to different extent depending on the cultivar, root zone, and metal concentration. The stimulating effect of Ni on oxidative burst in Cd-treated maize roots was related to an increased Cd-induced superoxide production. The cell death appeared between 24 and 48 h and between 12 and 24 h of the 10 μM and 100 μM metal treatments, respectively. This was in accordance with Cd-induced ROS (superoxide) production and the EM decline in the corresponding time periods. Cell viability, EM changes and partially superoxide production indicate that the impact of the metals on the studied parameters declined in the order Cd+Ni > Cd > Ni and that cv. Blitz tends to respond more sensitively than cv. Premia.