THE INFLUENCE OF THE FORM OF NITROGEN NUTRITION ON UPTAKE AND DISTRIBUTION OF CADMIUM IN LETTUCE VARIETIES

Four lettuce (Lactuca sativa L.) varieties ('Benita', 'Wendy', 'Mirena', and 'Jacky') were grown for 43 days in a pH-controlled complete nutrient solution without cadmium (Cd) or with either 0.01 or 0.03 mg Cd/l and with NH4 or NO3 as the form of nitrogen nutrition. Cadmium did not affect dry matter yield. 'Wendy' had a significantly higher total dry matter production when grown on NO3 compared to NH4, whereas growth of 'Mirena' was best on NH4 (P<0.05). Dry weights of 'Benita' and 'Jacky' were not affected by the N source. Cadmium concentrations in shoots (and roots) of plants grown on NH4 were significantly higher than in plants grown on NO3. The Zn concentrations in the shoots were also enhanced. The distribution of Cd in the lettuce varieties was independent of the form of N nutrition. It is concluded that the N source directly affects the amount of Cd taken up, without influencing the Cd distribution.