Plant and Soil

, Volume 221, Issue 1, pp 25–32

Influx, efflux and net uptake of nitrate in Quercus suber seedlings

  • Catarina Mata
  • Nicole van Vemde
  • David T. Clarkson
  • Maria Amélia Martins-Loução
  • Hans Lambers
Article

DOI: 10.1023/A:1004785331462

Cite this article as:
Mata, C., van Vemde, N., Clarkson, D.T. et al. Plant and Soil (2000) 221: 25. doi:10.1023/A:1004785331462

Abstract

Nitrate influx, efflux and net nitrate uptake were measured for the slow-growing Quercus suber L. (cork-oak) to estimate the N-uptake efficiency of its seedlings when grown with free access to nitrate. We hypothesise that nitrate influx, an energetically costly process, is not very efficiently controlled so as to avoid losses through efflux, because Q. suber has relatively high respiratory costs for ion uptake. Q. suber seedlings were grown in a growth room in hydroponics with 1 mM NO3-. Seedlings were labelled with 15NO3- in nutrient solution for 5 min to measure influx and for 2 h for net uptake. Efflux was calculated as the difference between influx and net uptake. Measurements were made in the morning, afternoon and night. The site of nitrate reduction was estimated from the ratio of NO3- to amino acids in the xylem sap; the observed ratio indicated that nitrate reduction occurred predominantly in the roots. Nitrate influx was always much higher than net acquisition and both tended to be lower at night. High efflux occurred both during the day and at night, although the proportion of 15NO3- taken up that was loss through efflux was proportionally higher during the night. Efflux was a significant fraction of influx. We concluded that the acquisition system is energetically inefficient under the conditions tested.

carbon budget efflux influx net uptake 15NO3- Quercus suber 

Copyright information

© Kluwer Academic Publishers 2000

Authors and Affiliations

  • Catarina Mata
  • Nicole van Vemde
  • David T. Clarkson
  • Maria Amélia Martins-Loução
  • Hans Lambers

There are no affiliations available

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