ISSN:
1432-2048
Keywords:
Nitrate (uptake, influx, efflux)
;
Nitrogen (limination)
;
Pisum
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Influx, efflux and net uptake of NO 3 − was studied in Pisum sativum L. cv. Marma in short-term experiments where 13NO 3 − was used to trace influx. The influx rate in N-limited plants was similar both during net uptake at external concentrations of around 50 μM, and at low external NO 3 − concentrations (4–6 μM) when net uptake was practically zero. Efflux could be inferred from discrepancies between influx and net uptake but was never very high in the N-limited plants during net uptake. Close to the threshold concentration for not NO 3 − uptake, efflux was high and equalled influx. Thus, the threshold concentration can be regarded as a NO 3 − compensation point. The inclusion of NH 4 + in the outer medium decreased influx by about 40% but did not significantly affect efflux. The roles of NO 3 − fluxes and nitrate-reductase activity in regulating/limiting NO 3 − utilization are discussed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00402990
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