EFFECT OF IRON PLAQUE ON ROOTS OF RICE ON GROWTH OF PLANTS IN EXCESS ZINC AND ACCUMULATION OF PHOSPHORUS IN PLANTS IN EXCESS COPPER OR NICKEL

Iron (Fe) plaque on roots of rice was found to lessen the toxic effect s of zinc (Zn). With excess Zn, plants with Fe plaque had significantl y greater dry mass of roots and foliage than plants without plaque. In the excess of Zn, plants with Fe plaque had higher concentrations of Fe but lower Zn than plants without plaque, although the differences w ere not significant. In the excess of copper (Cu) or nickel (Ni), plan ts with Fe plaque had significantly lower concentration of phosphorus (P) in leaves than plants without plaque. It is suggested that the low concentration of P in leaves of plants with plaque will increase the concentration of ''active iron'' inside leaves, and therefore, increas e their tolerance against heavy metal toxicity.