REDUCTION OF FE(III), MN(III), AND CU(II) CHELATES BY ROOTS OF PEA (PISUM-SATIVUM L) OR SOYBEAN (GLYCIAE MAX)

Neither the reduction of Fe(III) to Fe(II) by roots nor its induction by Fe-deficiency are unique characteristics of the reductive activitie s of roots. We show that chelated Mn(III) or chelated Cu(II), as well as chelated Fe(III), may be reduced by Fe-stressed roots of pea (Pisum sativum L.). Deficiency of Fe stimulated the reduction of Fe(III)EDTA about 20-fold, the reduction of Mn(III)CDTA about 11-fold, the reduct ion of Cu(II)(BPDS)(2) about 5-fold, and the reduction of Fe(III)(CN)( 6) by only about 50%. Not only are metals other than Fe reduced as par t of the Fe-stress response, but deficiencies of metals other than Fe stimulate the reductive activity of roots. We show that depriving peas or soybeans (Glycine max) of Cu or Zn stimulates the reduction of Fe( III).