Nitrogen nutrition of rice plants under salinity

Two rice (Oryza sativa L.) cultivars, Koshihikari and Pokkali, were grown in solution culture at three concentrations of NaCl or Na2SO4 [0 (S0), 50 (S1), and 100 (S2) mmol dm(-3)] and three N contents [0.7 (N1), 7 (N2) and 14 (N3) mmol dm(-3)]. Salinity significantly decreased dry matter of both cultivars. Pokkali had better growth than Koshihikari under both saline and non-saline conditions. Applications of N enhanced development of shoot dry mass under S0 and S1 treatments up to N2. Under S2, N application had no effect on shoot dry mass of both cultivars. Root dry mass of both cultivars decreased with increasing N application at S1 and S2. Shoot and root NO3-N content in both rice cultivars increased with increasing N concentration in the nutrient solutions. The absorption of NO3-N was less in Koshihikari than Pokkali plants, and also was much less in Cl- than SO42+ salinity suggesting the antagonism between Cl- and NO3-. In addition a significant negative correlation between concentrations of NO3-N and Cl-1 in the shoots or roots was observed in both cultivars.