Separation of soluble heavy metals in the roots of mulberry by Sephadex G-75 gel filtration

Abstract

Extracts from the roots of mulberry grown in water culture which was mixed with Cd, Zn or Pb were separated by Sephadex G-75 gel filtration to examine the form of heavy metals present in the soluble fraction of the roots. Cd appeared in 3 peaks (P1, P2 and P3) and Zn in 2 peaks (P1 and P3). Pb exhibited P4 (although small) in addition to P1, P2 and P3, where in P1 was the largest. P1 corresponded to the void volume of the gel column and thus Cd, Zn and Pb in P1 may be bound to components with molecular weights of more than 70, 000. The heavy metals appeared in P2 and P3 were considered to be bound to substances (proteins?) with molecular weights of about 3, 000 to 70, 000. Pb in P4 may be bound to low molecular weight components or in a free form. The ratio of the heavy metal concentration to A₂₅₀ of each peak was augmented according to the concentration of heavy metals in the culture media in which the plants were grown. The A250 values of P3 markedly dropped when the plant growth was inhibited by the heavy metals.