EFFECT OF NITROGEN ON THE GROWTH AND PHOTOSYNTHETIC ACTIVITY OF SALT-STRESSED BARLEY

Pot experiments were conducted in the greenhouse to study the effect of nitrogen (N) nutrition on photosynthesis and water relations of barley plants under salinity conditions. Nitrogen decreased the sodium (Na) content and increased the potassium (K) content in shoots. The net photosynthetic rate of leaves increased significantly with added N increasing from 0 to 100 mg N/kg soil. The activity of ribulose 1,5 bisphosphate carboxylase (RuBPCase) in leaves of high-salt plants was lower, and in leaves of the low-salt plants higher than that in control plants. The photosynthetic rate was reduced by sodium chloride (NaCl) and was significantly correlated with total soluble protein per unit leaf area. At each N level, stomatal conductance in leaves was reduced con- siderably by salt. Proline content of leaves increased with increasing N level. It was higher in leaves of salt-treated plants than in those of control plants. The osmotic potential of leaves decreased with increasing N applied, and the turgor pressure of high N plants remained higher under salt treatment condition.