Effects of Salinity and NO3:NH4 Ratio on Yield and Quality in Canola (Brassica napus L.)

Abstract

The effect of salinity and NO3: NH4 ratio (0:100, 75: 25, 50:50, and 25:75) in the nutrient solution on growth, yield quality and N metabolism in hydroponically grow canola (Brassica napus L.) was evaluation. Both fresh and dry weights of leaves were significantly lower when a high concentration of either NO3 (100%) or NH4 (75%) was the sole N source in the nutrient solution. In nonsaline condition, increasing of both NH4 and NO3 ratio in the nutrient solution reduced photosynthetic (pn) rate, however in salinity condition the reduction of pn became more pronounced at a higher ratio of NH4 in the nutrient solution. The yield in terms of fresh and dry weight of seed per plant was significantly increased at the 75:25 (NO3: NH4) treatments. Total fat in nonsaline condition was increased with increasing NH4 ratio in the nutrient solution, however in saline condition it was reduced, at high NH4 ratio in the nutrient solution. The increase of tissue N concentration was nearly proportional to the NH4 concentration in the nutrient solution.The activity of nitrate reductase (NR) was increased by increasing NH4 form 0 to 50% and then reduced at a higher ratio of NH4 in the solution. Salinity increased NH4 concentration so that the saline condition had nearly twice high NH4 concentration in the leaves. The increase of NH4 concentration induced by salinity could be parially the reduction of NH4 assimilate because of the shortage of carbohydrate.