Short-term studies of NO3−uptake inPisumusing13NO3−

✍ Scribed by P. Oscarson; B. Ingemarsson; M. af Ugglas; C. -M. Larsson

• Book ID: 104759092
• Publisher: Springer-Verlag
• Year: 1987
• Tongue: English
• Weight: 627 KB
• Volume: 170
• Category: Article
• ISSN: 0032-0935
• DOI: 10.1007/bf00402990

✦ Synopsis

Influx, effiux 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 gM, and at low external NO 3 concentrations (4-6 gM) 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 net NO 3 uptake, efflux was high and equalled influx. Thus, the threshold concentration can be regarded as a NO;-compensation point. The inclusion of NH~-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.