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Optimization of ammonium acquisition and metabolism by potassium in rice ( Oryza sativa L. cv. IR‐72)
Author(s) -
BALKOS KONSTANTINE D.,
BRITTO DEV T.,
KRONZUCKER HERBERT J.
Publication year - 2010
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.2009.02046.x
Subject(s) - phosphoenolpyruvate carboxylase , oryza sativa , ammonium , glutamine synthetase , chemistry , metabolism , shoot , potassium , photosynthesis , horticulture , biochemistry , botany , biology , glutamine , amino acid , organic chemistry , gene
We present the first characterization of K + optimization of N uptake and metabolism in an NH 4 + ‐tolerant species, tropical lowland rice (cv. IR‐72). 13 N radiotracing showed that increased K + supply reduces futile NH 4 + cycling at the plasma membrane, diminishing the excessive rates of both unidirectional influx and efflux. Pharmacological testing showed that low‐affinity NH 4 + influx may be mediated by both K + and non‐selective cation channels. Suppression of NH 4 + influx by K + occurred within minutes of increasing K + supply. Increased K + reduced free [NH 4 + ] in roots and shoots by 50–75%. Plant biomass was maximized on 10 m m NH 4 + and 5 m m K + , with growth 160% higher than 10 m m NO 3 ‐ ‐grown plants, and 220% higher than plants grown at 10 m m NH 4 + and 0.1 m m K + . Unlike in NH 4 + ‐sensitive barley, growth optimization was not attributed to a reduced energy cost of futile NH 4 + 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 NH 4 + is likely to be of substantial agronomic significance in the world's foremost crop species.