Use of perlite in cadmium plant studies: an approach to polluted soil conditions.

Two different types of hydroponic cultures, "water culture" and "perlite system", were compared using white lupin plants (Lupinus albus L., cv. Marta) under different Cd treatments: 0, 0.2, 0.6, 2, 4, 6, 13, 20, 40 and 60 microM (water culture) and 0.2, 2, 20, 60 and 150 microM (moistened perlite). Fresh weight, shoot and root length, and total Cd concentration in the plants were measured. Moreover, a batch experiment was carried out to study the ability of perlite to adsorb and desorb Cd from nutrient solution. Lupin plants under Cd treatments in "water culture" showed a higher growth inhibition than those grown on perlite. A high positive correlation between Cd concentration in the plant and Cd supply was obtained regardless of the substrate used. Moreover, a high positive correlation between Cd doses with the "perlite system" and their equivalent Cd doses estimated for the "water culture" system was observed. Thus, the "water culture-equivalent" Cd doses were 14 times lower than the Cd doses in the perlite system. On the other hand, desorbed Cd concentrations were calculated giving values 12 times lower than the tested Cd doses.