Nitrate Uptake
Nitrate must enter the cells before undergoing assimilatory reduction by the joint action of nitrate reductase and nitrite reductase. Cells accumulate NO-3 against concentration gradient and this accumulation is a result of the presence of active NO-3 transport system in the cell membrane.
Nitrate uptake and nitrate reduction are independent processes because organisms genetically deficient in nitrate reductase activity contain normal transport activity.