Effect of Different Ammonium: Nitrate Ratios on leaves Photosynthesis Rate and Fatty Acid Composition in Canola seeds under Salinity Stress

In order to investigate the effect of different ratios of ammonium: nitrate on the photosynthesis and fatty acid composition in canola leaves (Brassica napus. L) under different salinity stress, an experiment as a factorial experiment based on randomize complete design was conducted at Agricultural Research Center in East Azerbaijan in2008 The first factor was different ratios of nitrogen sources to ammonium: nitrate at four levels as 0/ 100, 25/ 75, 50/50 and 75/ 25 and the second factor was two levels of salinity as 0 and 200 mM NaCl. Results showed that the highest fresh and dry weights, leaf area and relative water content (RWC), photosynthesis rate and potassium concentration in the leaves were obtained at nitrate: ammonium (50/ 50) in non saline condition. With increasing salinity, fresh and dry weights, leaf area, relative water content (RWC), photosynthesis and leaf potassium were significantly reduced. The fatty acid compositions in different treatments were also evaluated. Application of high amounts of ammonium on canola caused more concentration of fatty acids than application of nitrate. The highest ratio of fatty acids was measured under salinity stress when application of nitrate: ammonium was at 25:75 level. It seems that under salinity stress the application of ammonium: nitrate ratio at 50/50 level caused less injury in crop