期刊
PLANT CELL AND ENVIRONMENT
卷 33, 期 1, 页码 23-34出版社
WILEY
DOI: 10.1111/j.1365-3040.2009.02046.x
关键词
cereals; channels; glutamine synthetase; influx; efflux; ion transport; nitrogen; phosphoenolpyruvate carboxylase
资金
- Canadian Green Crop Network (GCN)
- Natural Sciences and Engineering Research Council of Canada (NSERC)
- Canada Research Chair (CRC) program
We present the first characterization of K+ optimization of N uptake and metabolism in an NH4+-tolerant species, tropical lowland rice (cv. IR-72). 13N radiotracing showed that increased K+ supply reduces futile NH4+ cycling at the plasma membrane, diminishing the excessive rates of both unidirectional influx and efflux. Pharmacological testing showed that low-affinity NH4+ influx may be mediated by both K+ and non-selective cation channels. Suppression of NH4+ influx by K+ occurred within minutes of increasing K+ supply. Increased K+ reduced free [NH4+] in roots and shoots by 50-75%. Plant biomass was maximized on 10 mm NH4+ and 5 mm K+, with growth 160% higher than 10 mm NO3--grown plants, and 220% higher than plants grown at 10 mm NH4+ and 0.1 mm K+. Unlike in NH4+-sensitive barley, growth optimization was not attributed to a reduced energy cost of futile NH4+ cycling at the plasma membrane. Activities of the key enzymes glutamine synthetase and phosphoenolpyruvate carboxylase (PEPC) were strongly stimulated by elevated K+, mirroring plant growth and protein content. Improved plant performance through optimization of K+ and NH4+ is likely to be of substantial agronomic significance in the world's foremost crop species.
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