Nitrogen transport in intact corn roots

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Abstract
Nitrogen uptake in 6-day-old intact corn roots was investigated with 15N as a tracer. Ammonium nitrogen was clearly adsorbed on the root surface, but nitrate nitrogen was not. Ammonium nitrogen was strongly absorbed from the elongation zone, while nitrate nitrogen was absorbed from the elongation and the root-hair zones. The speed of the transport of nitrogen from the cortex to the stele at the apical and basal regions of the roots was different for ammonium and nitrate. At the apical region ammonium was faster than nitrate and at the basal region the opposite was the case. This was probably due to differences in the patterns of assimilation and translocation of the two nitrogen forms.