Cadmium accumulation and its effect on yield of lettuce, radish, and cucumber

Pot experiments were conducted on lettuce, radish, and cucumber plants under glasshouse conditions to study the effects of increasing cadmium (Cd) application on yields and Cd concentration in the edible plant parts. Cadmium was applied to the pot medium (peat-soil mixture) at 0, 1, 5, 10 and 20 mg/kg. Although toxicity symptoms were not observed in any plant the Cd concentration of the edible plant parts of all the experimental material was increased by Cd treatment in a relationship characterized by a quadratic regression. Lettuce yield was suppressed at rates of Cd application higher than 10 mg/kg whereas in radish and cucumber yields were not affected by Cd application. Cadmium accumulation occurred in lettuce and cucumber edible parts and in the former the "outer" leaves accumulated 5-43% more Cd than the "inner" leaves. Diethylene triamine penta acetic acid-triethanol amine (DTPA-TEA) extractable Cd significantly correlated with the Cd concentration in lettuce leaves and the flesh and skin of cucumber fruits indicating that this extractant could be used to predict Cd concentration in the edible parts of these two crops.