The objective of this work was to evaluate the influence of Mg in the absorption of Mn and Zn in four soybean cultivars. Excised roots were used in the assays of absorption kinetics. The roots were placed in solutions with the following combinations: three concentrations of Mg (1.0, 3.0 and 6.0 mmol L-1) x five concentrations of Zn or Mn (0.5, 1.0, 2.0, 5.0 and 10.0 mumol L-1), with three replicates. To each of these solutions 14.8 MBq of radiozinc or radiomanganese was pipetted. After one hour of exposure, the roots were washed, ovendried, weighted, and the absorbed radioactivity determined. The obtained values were converted to micromoles per gram of dry matter. The Km and Vmax estimated values were determined by the Lineweaver & Burk transformation. The soybean cultivars showed an effect of noncompetitive inhibition between Mg and Zn and between Mg and Mn. The cultivars had distinct behavior in absorption of Mg, Mn and Zn. The Km and Vmax values were mutually independent in the absorption process of roots.
Glycine max; nutrient; inhibition; mineral deficiency
