MECHANISM OF HEAVY METAL TOLERANCE IN FEW PLANTS,MULBERRY DND OTHERS

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Heavy metal tolerant plant, Athyrium yokoscense and sensitive plants, mulbeey and kidneybean were cultivated in water solution containing Cd at 10^<-6>-10^<-3>M for 3 days and heavy metal contents in plant organs were measured. And individual organs were fractioned by centrifuged at 200xg, 700xg, 10,000xg for 30min after grind in Tris HCl buffer (pH7.8) containing 0.25M succrose.[result] Nutrient uptake did not fall rapidly as the ascent of Cd concentration in Athyyrium yokoscense, but it fell rapidly in mulberry and soybean. Cd content in roots in A.Yokoscense was lower than that in mulberry and soybean treated with lower concentration of Cd. But the difference among plants was not observed treated with higher Cd concentration.Cd in the F1 raction of roots was more than 90% of the whole in A.yokoscence but 55-70% in kidneybean and 30-50% in mulberry. It was considered that Cd was catched by cell wall at first in the tolerant plant and the inhibition by Cd was weakened.Monoploid, dipoid and tetraploid plants were grown by the culure of shoot apex and cultiivated in water solutions containing 5,10,15 and 20muM Cd. Inhibition cofficient of dry weight growth was measured. And fractination was performed by the method as above-mentioned.[result] Differnce of tolerance among pollyploids were observed, monoploid>dipolid>tetraploid. Cd content in the F1 fraction was monoploid>dipolid>tetraploid. This order agreed with that of tolerance.