Journal of Plant Process and Function

In order to investigate the interaction effect of salinity and nitrogen on growth, mineral composition and salinity tolerance of soure orange seedlings a factorial experiment was carried out in completely randomized design with three replications. Factors consisted of four sodium chloride rates (0, 250, 500 and 1000 mg sodium chloride kg^-1 soil) and four nitrogen levels (0, 50, 100, and 200 mg N kg^-1 soil as ammonium sulfate). Sodium and chloride ions concentration in plant shoot and root were increased to toxic levels as the sodium chloride rates were increased form 0 to 1000 mg kg^-1 soil. Subsequent result of this event was the significant reduction in plant dry weight. In all sodium chloride rates, nitrogen consumption up to 100 mg kg^-1 soil increased plant dry weight. However the increasing effect of nitrogen on plant growth was dependent on applied sodium chloride level. As the level of applied sodium chloride was increased, the improvement effect of nitrogen on plant growth was decreased. Although nitrogen had no conciderable effect on sodium concentration in plant shoot and root, increments in nitrogen application made a decrease in shoot chloride concentration and an increase in root concentration of this element. Salinity decreased nitrogen, phosphorus, potassium, iron, manganese, zinc and copper concentration in plant shoot. So it can be concluded that the salinity influence on plant growth reduction can partly be related to the decrease of essential nutrients concentration to below sub optimal levels. Nitrogen improved the decreasing effect of salinity on concentration of plant essential nutrients by increasing their concentration in plant tissues. Therefore it can be concluded that under salinity condition, part of nitrogen influence on reduction of salinity adverse effects is related to the maintenance of essential nutrients concentration in plant tissues.