Figure 6.

Unidirectional influx of ${\text{NO}}_3^{-}$ (A) and ${\text{NH}}_4^{+}$ (C) into the roots of maize genotypes grown at either 0.5 mM or 2.5 mM ${\text{NO}}_3^{-}$. Nitrate and ${\text{NH}}_4^{+}$ influx were measured using¹⁵N labeled ${\text{NO}}_3^{-}$ or ${\text{NH}}_4^{+}$ over a 10-min influx period from a 200 μM solution. Values are predicted values ± standard error (n = 4) ^* indicates those points that are significantly different between the two growth conditions at 0.05 significance level. Genotypes are ordered from left to right according to their ability to retain biomass as shown in Figure 2. Missing values for ${\text{NH}}_4^{+}$ flux are due to no measurement of ${\text{NH}}_4^{+}$ flux being made on these lines. Scatterplots (B,D) are the ratio of the values at each nitrate concentration plotted against their ability to retain biomass.