Combined effects of salinity and nitrogen levels on some physiological and biochemical aspects at the halophytic forage legume Sulla carnosa

Salinity and low nitrogen availability are two major abiotic stresses that often coexist and disturb plant productivity. This study aimed at investigating the combined effects of salinity (0 and 100 mM NaCl) and nitrogen (0.5 and 5.0 mM NH4NO3) levels on the morphological parameters, the mineral status, nitrogen use efficiency, photosynthesis, and nitrate reductase (NR, E.C. 1.6.6.1) and glutamine synthetase (GS, EC 6.3.1.2) activities at Sulla carnosa.left-to-right mark Salinity enhanced growth rate (66%), the relative growth rate (RGR), root volume (RV), Na+ and Cl- accumulations and nitrogen use efficiency (NUE). It had no detrimental effect on photosynthetic assimilation rate (A) and leaf NR and GS activities under high nitrogen level condition. High nitrogen availability under saline condition enhanced growth rate, RGR, shoot/root ratio, photosynthesis activity, NR activity in roots, and the accumulation of NO3- in different plant organs and all cations and anions in roots. In brief, salinity and high nitrogen availability represented an adequate condition for optimal growth and high Na+ and NO3- accumulations at S. carnosa. This study suggested that S. carnosa could be a suitable forage legume that can be widely cultivated in the discarded, salinized and nitrogen-contaminated agricultural soils.