Utilize este identificador para referenciar este registo: http://hdl.handle.net/10451/4268
Título: Influx, efflux and net uptake of nitrate in Quercus suber seedlings
Autor: Mata, Catarina
Vemde, Nicole van
Clarkson, David T.
Martins-Loução, Maria Amélia
Lambers, Hans
Palavras-chave: Carbon budget
Efflux
Influx
Net uptake
15NO-3
Quercus suber
Data: 2000
Citação: Plant and Soil 221: 25–32, 2000
Resumo: 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 hydroponicswith 1 mM NO- 3 . Seedlings were labelled with 15NO- 3 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 NO- 3 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 15NO- 3 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.
Descrição: ACESSO via B-on: http://dx.doi.org/doi:10.1023/A:1004785331462
Peer review: yes
URI: http://dx.doi.org/doi:10.1023/A:1004785331462
http://hdl.handle.net/10451/4268
ISSN: 0032-079X
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