Effect of NaCl salinity on nitrate uptake in Plantago maritima L.

Exposure of plants to NaCl salinity reduces the rate of nitrate net uptake by the roots. Previous studies showed that this effect was due to a reduced nitrate influx, which could only partially be explained by a lower demand of nitrate for growth. In the present work we tested the hypothesis that the observed decrease in nitrate net uptake rate is specific for nitrate and that this effect is due to a competitive or non-competitive inhibition of the nitrate transport system at the root plasma membrane. We conclude that NaCl induced reduction in nitrate net uptake rate was specific as it did not affect the uptake of other anions such as sulphate or phosphate. We could rule out that competitive or non-competitive inhibition of the nitrate transport system by external Cl- was responsible for the reduction of nitrate influx.