Effects of aluminium on nitrate uptake and assimilation
1995
Rufty, T.W. Jr | MacKown, C.T. | Lazof, D.B. | Carter, T.E.
A study was conducted to examine the hypothesis that the effects of external Al on NO3(-) uptake and assimilation depend upon the concentration of Al present. Young soybean seedlings [Clycine max (L.) Merrill, cv. Essex], growing under moderate acidity stress at pH 4.2, were exposed to a range of (Al3+) in solution for 3 d, and to labelled 99 atom % 15NO3(-) during the final hour of Al exposure. Uptake of 15NO3(-)g-1 root dry weight was increased by about 28% in the presence of Al at (Al3+) below 10 mmol m-3, and NO3(-) uptake was decreased by about 12% when the (Al3+) increased to 44 mmol m-3. The stimulation phase closely paralleled stimulation of root elongation. At higher (Al3+), the inhibition of root elongation was much more severe than that of NO3(-) uptake. There was no indication of a separate effect of Al on root 15NO3(-) reduction in situ, as the accumulation of reduced 15N in the root remained a similar percentage of 15NO3(-) uptake at all (Al3+). At higher (Al3+) the atom % 15N enrichment of the insoluble reduced-N (protein) fraction of root tips increased. This suggests that the Al inhibition of root elongation did not result from disruption of the N supply to the root apex.
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