Comparison of the cadmium, zinc, manganese and copper concentrations in shoots and roots during the early growth period of two cultivars of Japanese radish grown on cadmium-contaminated soil

摘要

A pot culture experiment was conducted to investigate the cadmium, zinc, manganese and copper concentrations of two Japanese radish cultivars(Raphanus sativus L.cv. Harunomegumi and Raphanussativus L. cv. Akibutai)grown for 9 weeks in soil whose respective cadmium and zinc concentrations were 3.3 and 68 mg/kg of dried soil. Both of the Japanese radish cultivars grew normally throughout thegrowth period, the weight of the shoots being 2.8 times that of the roots. The cadmium concentrations in the shoots of both cultivars initially increased for 6 weeks after sowing and then slowed. The cadmium concentrations in the shoots after 9 weeks or growth were respectively 2.4 and 1.5 mg/kg for Harunomegumi and Akibutai, this 0.9 mg/kg diference indicating cultivar dependence. The cadmium concentrations in the roots of both cultivars were about one fourth of those of the shoots. The zinc,manganese and copper concentrations varied similarly for both of the cultivars. The zinc concentrations in the shoots did not fluctuate greatly at between 20 and 50mg/kg, this being similar to the zincconcentrations in the roots throughout the growth period. The manganese concentrations in the shoots increased from around 2 to 12 mg/kg during the growth period, while those in the roots remained almost constant at around l.5 mg/kg. The copper concentrations in the shoots tended to be higher than those in the roots throughout thr egrowth period. The copper concentration in the shoots after 9 weeks of growth was around l.2 mg/kg, being 1.4 times that in the roots.