A kinetic analysis of cadmium accumulation in a Cd hyper‐accumulator fern, A thyrium yokoscense and tobacco plants

Cadmium ( Cd ) accumulations in a Cd hyper‐accumulator fern, A thyrium yokoscense ( Ay ), and tobacco, N icotiana tabacum ( Nt ), were kinetically analysed using the positron‐emitting tracer imaging system under two medium conditions (basal and no‐nutrient). In Ay , maximumly 50% and 15% of the total Cd accumulated in the distal roots and the shoots under the basal condition, respectively. Interestingly, a portion of the Cd in the distal roots returned to the medium. In comparison with Ay , a little fewer Cd accumulations in the distal roots and clearly higher Cd migration to the shoots were observed in Nt under the basal condition (maximumly 40% and 70% of the total Cd , respectively). The no‐nutrient condition down‐regulated the Cd migration in both species, although the regulation was highly stricter in Ay than in Nt (almost no migration in Ay and around 20% migration in Nt ). In addition, the present work enabled to estimate physical and physiological Cd accumulation capacities in the distal roots, and demonstrated condition‐dependent changes especially in Ay . These results clearly suggested occurrences of species‐/condition‐specific regulations in each observed parts. It is probable that integration of these properties govern the specific Cd tolerance/accumulation in Ay and Nt .