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Gynura divancata (L.) DC. is a perennial herbaceous plant mainly distributed in the south and southwestern of China and Taiwan. At present, few report about its N nutrition and relating information have been found. In this study, Gynura divancata was taken as experiment materials to explore different nitrogen supply level on yield and quality of the plant using solution culture method and combining 15N isotope tracer technology. By using different nitrogen forms and ratios based on the best nitrogen supply concentration, to investigete the best ratio of NH4+/NO3-. Through analysis of NO3-content and NH4+content, NR, GS, GOGAT and GDH activity, and hormones contents, in root, stem and leaf of Gynura divancata, to study internal nitrogen metabolism mechanism of Gynura divancata for providing theoretical basis of rationally fertilization and soilless culture.The main results are as follows:1. The effects of different nitrogen levels on yield, nitrate content, and nutrition quality of Gynura divancata were investigated under hydroponics. At 10-14mmol·L yield, vitamin C, free amino acid, protein content are relatively high, flavone medium, nitrate contents and activity of nitrate reductase relatively low. Taking yield and quality as measurement index, the optimal nitrogen concentration for Gynura divancata under hydroponics is 10-14mmol·L-1.2. In the nitrogen concentration of 12 mmol·L-1, the effects of different nitrogen forms and ratio on yield, grow, plant hormone and nutrition quality of Gynura divancata were investigated under hydroponics. The result showed that with the increase of NH4+ and the drop of NO3-, the height of plant, length of root, fresh weight and dry weight, yield, soluble sugar content, soluble protein content and flavone content are increased at the beginning, then decline. However, plant hormones and mineral element have shown inconsistent.3. Study on the effects of different nitrogen forms and ratio on nitrate and nitrite content, NR activity, GS activity, GOGAT activity and GDH activity. The result showed that with the increase of NO3- and the drop of NH4+, nitrate and nitrite content and NR activity in leaf are always a tendency to increase, GOGAT and GDH activity are up at the beginning, then decline, when NH4+:NO3- is 75:25 the result is biggest, and GS activity is rapidly increase, then slowly decline. 4. Culture Gynura divancata through nutrient solution with 15N mark NH/and NO3-and with different ratio of NH4+and NO3-". The result showed that nitrogen forms have significant influences on dry matter accumulation, quantity and nitrogen utilization efficiency, treatment in NH4+NO3-=25:75 is highest.15N accumulation in plant is leaf> stem> root, and 15N accumulation quantity in root close to 15N accumulation quantity of stem, but N accumulation quantity in leaf higher than the sum of root and stem. With increase of NH4+and drop of NO3-, nitrogen utilization efficiency becomes higher at the beginning, then decline, NH4+NO3-=25:75 is the highest than other treatment which reached 31.25%, and treatment in NH4+:NO3-=100:0 is the lowest, only 12.1%.5. This experiment suggest the suitable nitrate concentration is 12 mmol·L-1 and NO3-:NH4+=75:25 for rational basis for rational fertilization and soilless culture.
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