Ameliorative Effect of Ammonium Sulfate on Salt Tolerance and Ion Homeostasis in Lemon (C. limon) Seedlings

To investigate interaction effects of salinity and nitrogen on growth, mineral composition and salinity tolerance of lemon seedlings, a greenhouse experiment with four sodium chloride concentrations (0, 250, 500 and 1000 mg kg-1 soil) and four nitrogen levels (0, 50, 100, and 200 mg kg-1 soil ammonium sulfate) was carried out. Experiment was conducted in a completely randomized design with three replications. Sodium and chloride ions in plant tissues were increased to toxic levels with increase in salinity which resulted in a significant reduction of plant dry weight. Nitrogen consumption up to 100 mg kg-1 soil increased plant dry weight. As the concentration of sodium chloride was increased, the improvement effect of nitrogen on plant growth was decreased. Although nitrogen had no considerable effect on sodium concentration in root and shoot, it made a decrease in chloride concentration in shoot and an increase in root concentration of this element. Salinity decreased essential nutrients concentration in plant shoot. Therefore, it can be concluded that adverse effect of salinity is to some extent due to reduction of required elements to suboptimal ranges in plant tissues. Nitrogen improved the adverse effects of salinity on plant nutrients by increasing their concentration in plant tissues. Therefore it can be inferred that part of the ameliorative effects of nitrogen on salinity adverse effects is related to the maintenance of essential nutrient concentrations in plant tissues. The results of the present study indicate that nitrogen can be applied in amounts higher than optimal level to reduce the harmful effects of salinity.          

Keywords:

Dry Weight , Ion Accumulation , Salinity stress