Effects of sulfur and salicylic acid on nitrate accumulation and nitrogen metabolism in leaves of Chinese chive

Effects of sulfur (S) and exogenous salicylic acid (SA) on accumulation of nitrate, the key enzyme activities of nitrogen metabolism and chlorophyll fluorescence of Chinese chive were studied to understand the effects of S and SA on nitrate accumulation and nitrogen metabolism. The results indicate that there are significant concentration effects on the fresh weight, nitrate content, the activity of nitrate reductase（NRA）, the maximal photochemical efficiency （Fv/Fm）, the apparent electron transport rate （ETR）and soluble protein content in Chinese chive. Compared with the control, the nitrate content with 7.2 kg/ha S and 3 mmol/L SA treatment is reduced by 16.6%, while the fresh weight of Chinese chive, NRA, Fv/Fm, ETR and soluble protein content are increased by 10.7%, 12.3%, 10.1%, 21.2% and 4.2%, respectively. The activities of glutamicoxaloacetic transaminase （GOT） and the glutamatepyruvatetransaminase （GPT） are increased gradually with the increase of S concentration. The GOTA and GPTA are highest under S 54 kg/ha and are increased by 13.6% and 9.4% respectively compared with the control. In conclusion, S and SA obviously improve nitrate reduction and assimilation, which, meanwhile, bring transaminations into play vigorously, and promote turning NO-3 into free amino acid and dissolvable protein. Improvement of nitrate reduction and assimilation might be a key reason for reducing nitrate accumulation into the vacuole of Chinese chive.