bio-accumulation of lead and cadmium by radish (raphanus sativus) and cress (lepidium sativum) under hydroponic growing medium

In order to investigate the accumulation and bio-absorption of lead and cadmium in radish and cress, the present study has been conducted in a completely randomized design in three replicates in a hydroponic growing medium. the first factor includes the plant type at two levels (radish and cress), and the second factor is consisted of lead (pb) (first experiment) at two levels (50 and 100 mg/l), cadmium (cd) (second experiment) at one level (10 mg/l), and a combination of lead and cadmium (third experiment) again at two levels. after 23 days, roots and aerial parts of both plants have been dried for 48 hours at 70°c in an oven. then, half gram (0.5 g) of the dried templates has been used to measure the accumulation of pb and cd by means of an atomic absorption spectrometer. the highest amount of pb in radish and crest roots belong to 100 mg/l concentration and the combined cd (10) + pb (100) mg/l treatment, respectively, and the highest amount of cd occurs in cd (10) + pb (50) for radish roots and in cd (10) + pb (100) combination for cress. moreover, the translocation factor (tf), with a value below 1 and higher bio-concentration factor (bcf) in roots, compared to the aerial part of both radish and cress, seem to be due to the low capability of these plants to transfer pb and cd from roots to aerial part. there is a high potentiality for lead accumulation in the roots that prevent its transfer to the aerial part.