Responses of bean and tomato plants to cadmium : Growth, mineral nutrition, and nitrate reduction

Abstract

The effects of Cd on growth, mineral content and nitrate reductase (EC. 1.6.6.1) activity of 17-day-old bean (Phaseolus vulgaris L. cv. Morgane) and tomato (Lycopersicon esculentum Mill. cv. Ibiza F 1 ) plants treated for 7 days with nutrient solutions containing 0 to 50 μM CdCl 2 were studied. The Cd treatment had a greater depressive effect on shoot and root dry weight production in bean than in tomato plants. Accumulation of Cd in the roots exceeds by far that of shoots, with the greatest Cd accumulation occurring in tomato plants. Increasing Cd supply resulted in a decrease of the Ca 2+ , K + , NO - 3 and reduced nitrogen contents of the tissues compared to control plants. Nitrate reductase activity from roots and leaves of Cd treated plants was reduced more in bean than in tomato. Cd-induced decrease in nitrate reductase activity was accompanied by a similar decrease in tissue NO - 3 concentrations. Therefore, this decrease is interpreted as being indirect, i.e. the consequence of the reduced NO - 3 uptake and translocation in the plants. The results are discussed with regard to Cd tolerance differences between the two species.