Cadmium uptake, tissue localization and structural changes induced at cellular level are essential to understand Cd tolerance in plants. In this study we have exposed plants of Pteris vittata to different concentrations of CdCl2 (0, 30, 60, 100 μM) to evaluate the tolerance of the fern to cadmium. Cadmium content determination and its histochemical localization showed that P. vittata not only takes up, but also transports and accumulates cadmium in the aboveground tissues, delocalizing it mainly in the less bioactive tissues of the frond, the trichomes and the scales. Cadmium tolerance in P. vittata was strictly related to morphogenic response induced by the metal itself in the root system. Adaptive response regarded changes of the root apex size, the developmental pattern of root hairs, the differentiation of xylem elements and endodermal suberin lamellae. All the considered parameters suggest that, in our experimental conditions, 60 μM of Cd may represent the highest concentration that P. vittata can tolerate; indeed this Cd level even improves the absorbance features of the root and allows good transport and accumulation of the metal in the fronds. The results of this study can provide useful information for phytoremediation strategies of soils contaminated by Cd, exploiting the established ability of P. vittata to transport, delocalize in the aboveground biomass and accumulate polluting metals.

Pteris vittata is known as an arsenic hyperac-\ud cumulator, but there is little information about its tolerance\ud to cadmium and on its ability to accumulate this heavy\ud metal. Our aim was to analyse the accumulation capacity,\ud oxidative stress and antioxidant response of this fern after\ud cadmium treatments. Cadmium content, main markers of\ud oxidative stress and antioxidant response were detected in\ud leaves of plants grown in hydroponics for both short-\ud (5 days) and long- (15 days) term exposure to 0 (control)\ud 60 and 100 lM CdCl2. In leaves, the concentration of\ud cadmium and oxidative stress were parallel with the\ud increase of cadmium exposure. In the short-term exposure,\ud antioxidant response was sufficient to contrast cadmium\ud phytotoxicity only in 60 lM cadmium-treated plants. In the\ud long-term exposure all treated plants, in spite of the\ud increase in activity of some peroxide-scavenging enzymes,\ud showed a significant increase in oxidative damage. As in\ud the long-term stress markers were comparable in all treated\ud plants, with no clear correlation with hydrogen peroxide\ud content, at least part of cadmium-induced oxidative injury\ud seems not mediated by H2O2. Based on our studies,\ud P. vittata, able to uptake relatively high concentrations of\ud cadmium, is only partially tolerant to this heavy metal

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