The aim of this study was to determine the physiological response and the defensive potential in species Asplenium scolopendrium L. and Dryopteris filix-mas (L.) Schott under the action of nickel. The following experimental variants were tested: 0, 250, 500, 1000, 1500 mg Ni kg-1soil. One month, and three months respectively, after the initiation of the experiment, the amount of assimilating pigments was determined. One month after the initiation of the experiment, there were no significant differences between the variants with Ni and the control as far as the content of chlorophyll (a and b) and carotenoids was concerned. The results obtained three months after the inception of the experiment indicate that, at low concentrations, Ni stimulates the synthesis of chlorophyll. In the same period there occurred antioxidant mechanisms: increase in the amount of carotenoids and increased activity of catalase. In the species Dryopteris filix-mas, the variant with 1.000 mg Ni kg-1soil, the amount of chlorophyll was significantly reduced, and the catalase activity was 3 times higher than that obtained in the control group.