EFFECT OF CADMIUM AND ZINC INTERACTION ON METAL UPTAKE AND REGENERATION OF TOLERANT PLANTS IN LINSEED

The effect of cadmium and zinc interactions in lowering cadmium toxici ty and in regeneration of tolerant plantlets from in vitro cultures of Linum usitatissimum (linseed) was monitored. Although zinc and cadmiu m are toxic at different concentrations, the interaction of these two ions at equimolar concentration can overcome the toxicity of cadmium. Tolerant plantlets can be regenerated in a culture medium containing b oth metals, The tolerant plantlets grew favourably in Cd2+ and Zn2+ se parately. The regenerants showed greater uptake of cadmium in the root s than shoots, whereas zinc was found to be translocated from roots to shoots. Estimation of metal uptake inside the cells demonstrated the accumulation of cadmium into the cytoplasm in the regenerated roots, w hereas more zinc was localised in the cell walls. In the regenerated s hoots, however, an equal amount of zinc was found in the cell wall and the cytoplasm. The study of a stress-induced enzyme, peroxidase, in t he regenerating tissues showed less activity in cadmium and zinc combi nation sets, indicating less stress in these tolerant regenerants.