Abstract
The time course of 13NH4+ uptake and the distribution of 13NH4+ among plant parts and subcellular compartments was determined for 3-week-old rice (Oryza sativa L. cv M202) plants grown hydroponically in modified Johnson's nutrient solution containing 2,100, or 1000 [mu]M NH4+ (referred to hereafter as G2, G100, or G1000 plants, respectively). At steady state, the influx of 13NH4+ was determined to be 1.31, 5.78, and 10.11 [mu]mol g-1 fresh weight h-1, respectively, for G2, G100, and G1000 plants; efflux was 11, 20, and 29%, respectively, of influx. The NH4+ flux to the vacuole was calculated to be between 1 and 1.4 [mu]mol g-1 fresh weight h-1. By means of 13NH4+ efflux analysis, three kinetically distinct phases (superficial, cell wall, and cytoplasm) were identified, with t1/2 for 13NH4+ exchange of approximately 3 s and 1 and 8 min, respectively. Cytoplasmic [NH4+] was estimated to be 3.72, 20.55, and 38.08 mM for G2, G100, and G1000 plants, respectively. These concentrations were higher than vacuolar [NH4+], yet 72 to 92% of total root NH4+ was located in the vacuole. Distributions of newly absorbed 13NH4+ between plant parts and among the compartments were also examined. During a 30-min period G100 plants metabolized 19% of the influxed 13NH4+. The remainder (81%) was partitioned among the vacuole (20%), cytoplasm (41%), and efflux (20%). Of the metabolized 13N, roughly one-half was translocated to the shoots.
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- Bloom A. J., Chapin F. S. Differences in steady-state net ammonium and nitrate influx by cold- and warm-adapted barley varieties. Plant Physiol. 1981 Nov;68(5):1064–1067. doi: 10.1104/pp.68.5.1064. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Breteler H., Nissen P. Effect of exogenous and endogenous nitrate concentration on nitrate utilization by dwarf bean. Plant Physiol. 1982 Sep;70(3):754–759. doi: 10.1104/pp.70.3.754. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Cooper A. J., Gelbard A. S., Freed B. R. Nitrogen-13 as a biochemical tracer. Adv Enzymol Relat Areas Mol Biol. 1985;57:251–356. doi: 10.1002/9780470123034.ch4. [DOI] [PubMed] [Google Scholar]
- Glass A. D., Thompson R. G., Bordeleau L. Regulation of NO(3) Influx in Barley : Studies Using NO(3). Plant Physiol. 1985 Feb;77(2):379–381. doi: 10.1104/pp.77.2.379. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hole D. J., Emran A. M., Fares Y., Drew M. C. Induction of nitrate transport in maize roots, and kinetics of influx, measured with nitrogen-13. Plant Physiol. 1990 Jun;93(2):642–647. doi: 10.1104/pp.93.2.642. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Lavoie N., Vézina L. P., Margolis H. A. Absorption and assimilation of nitrate and ammonium ions by jack pine seedlings. Tree Physiol. 1992 Sep;11(2):171–183. doi: 10.1093/treephys/11.2.171. [DOI] [PubMed] [Google Scholar]
- Roberts J. K., Pang M. K. Estimation of Ammonium Ion Distribution between Cytoplasm and Vacuole Using Nuclear Magnetic Resonance Spectroscopy. Plant Physiol. 1992 Nov;100(3):1571–1574. doi: 10.1104/pp.100.3.1571. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Sasakawa H., Yamamoto Y. Comparison of the uptake of nitrate and ammonium by rice seedlings: influences of light, temperature, oxygen concentration, exogenous sucrose, and metabolic inhibitors. Plant Physiol. 1978 Oct;62(4):665–669. doi: 10.1104/pp.62.4.665. [DOI] [PMC free article] [PubMed] [Google Scholar]