Table II.

Component fluxes of NO₃⁻ as determined by compartmental analysis

Treatment	Φoc		Φco		Φnet		Φred/vac		Φ*xylem
	−	+	−	+	−	+	−	+	−	+
	μmol g−1 h−1
0.1 mm NO3−	8.61  ± 0.77	5.77  ± 0.59	0.57  ± 0.02	0.84  ± 0.13	7.57  ± 0.76	4.93  ± 0.7	5.3  ± 0.6	3.49  ± 0.62	2.27  ± 0.25	1.44  ± 0.1
1.0 mm NO3−	12.93  ± 0.88	10.02  ± 0.13	1.6  ± 0.56	1.46  ± 0.36	11.33  ± 1.44	8.55  ± 1.06	6.85  ± 1.22	5.86  ± 1.08	4.47  ± 0.22	2.69  ± 0.02
10 mm NO3−	20.94  ± 0.73	21.58  ± 0.57	10.56  ± 3.97	12.14  ± 0.98	10.38  ± 4.7	9.44  ± 1.54	6.68  ± 2.08	5.95  ± 1.76	3.7  ± 2.62	3.49  ± 2.17
Uninduced	0.53  ± 0.12	0.48  ± 0.04	0.07  ± 0.01	0.13  ± 0.01	0.46  ± 0.1	0.34  ± 0.02	0.36  ± 0.07	0.28  ± 0.03	0.096  ± 0.03	0.055  ± 0.005
NO2− induced	8.1  ± 0.69	7.16  ± 0.74	0.29  ± 0.02	0.47  ± 0.09	7.8  ± 0.75	6.69  ± 0.49	6.67  ± 0.62	5.46  ± 0.49	1.13  ± 0.22	1.23  ± 0.09

Barley plants were exposed to and labeled at the indicated concentrations of NO₃⁻ for 24 h prior to experiments. Uninduced plants were grown in N-free solution but exposed to 0.1 mm NO₃⁻ during labeling and elution. “NO₂⁻-induced” plants were exposed to 0.1 mm NO₂⁻ for 24 h prior to labeling and elution at 0.1 mm NO₃⁻. NH₄⁺ was present at 1.0 mm during labeling and elution in + treatments. Data are ±se (n ≥ 6).