1994 journal article
INFLUENCE OF NITRATE ON UPTAKE OF AMMONIUM BY NITROGEN-DEPLETED SOYBEAN - IS THE EFFECT LOCATED IN ROOTS OR SHOOTS
JOURNAL OF EXPERIMENTAL BOTANY, 45(280), 1575–1584.
In non-nodulated soybean [Glycine max (L.) Merrill cv. Ransom] plants that were subjected to 15 d of nitrogen deprivation in flowing hydroponic culture, concentrations of nitrogen declined to 1.0 and 1.4 mmol Ng −1 dry weight in shoots and roots, respectively, and the concentration of soluble amino acids (determined as primary amines) declined to 40 μmol g −1 dry weight in both shoots and roots. In one experiment, nitrogen was resupplied for 10 d to one set of nitrogen-depleted plants as 1.0 mol m −3 NH 4 + to the whole root system, to a second set as 0.5 mol m −3 NH 4 + plus 0.5 mol m −3 NO 3 − to the whole root system, and to a third set as 1.0 mol m −3 NH 4 + to one-half of a split-root system and 1.0 mol m −3 NO 3 − to the other half