Table I.

Kinetic parameters for high-affinity root Mn2+ influx in 10-d-old plants of the barley genotypes Antonia (Mn inefficient) and Vanessa (Mn efficient)

Values for Vmax and the apparent Km were obtained by fitting calculated data of root Mn influx at external Mn2+ concentrations ranging from 0.1–7.8 nm to the Michaelis-Menten equation using nonlinear regression analysis (Fig. 3). Root DWs (P > 0.05) were 28.3 and 26.7 mg for Vanessa and Antonia, respectively, and the corresponding shoot DWs were 133 and 125 mg, both being nonsignificant. For both genotypes, the Mn concentration in the roots was approximately 70 μg g−1 DW. Values with the same superscript letter were not significantly different between genotypes. The results are means ± 95% confidence limits of four independent regressions (n = 4).

HATSVmaxKmRegression Coefficient
nmol Mn g −1 DW h−1nmR2
Antonia1.4 ± 0.4b2.7 ± 1.6a0.998
Vanessa5.4 ± 1.0a5.4 ± 1.8a0.980