| In this research, on the one hand, the growth and nutrition metabolism of Robinia pseudoacacia were investigated by inoculating with the arbuscular mycorrhizal fungi(AMF) under different nitrogen levels in sterilized soil. Pot culture and experimental analyses -were carried out. On the other hand, 15N labeling was used to determine nitrogen Ndff%, distribution rate, nitrogen use efficiency and nitrogen balance after fertilization and inoculated, and after fertilized for the two groups of Robinia pseudoacacia seedlings that the growth time respectively was 50 d and 100 d, the key enzyme activities of carbon-nitrogen metabolism and rhizosphere soil at different stages were studied. The main points of this dissertation are as follows:1. Effects of nitrogen and AM fungi on the growth and nutrition metabolism of Robinia pseudoacacia.After inoculated AM fungi, the colonization, root system vigor, biomass, leaf superoxidedismutase (SOD), catalase (CAT) and nitrate reductase (NR) activity were significantly increased by inoculating with AM fungi,then decreased by the increasing nitrogen levels,and the best level was 0.4 g·kg-1. The contents of malondialdehyde (MDA) and proline (PRO) were decreased first and then increased by the increasing nitrogen levels, and the least level was 0.4 g·kg-1. Effects of mycorrhiza varied by different AM fungi. Inoculation with G. mosseae has a significant correlation with infection rate and other indice,which promoted the growth and nutrition metabolism of Robinia pseudoacacia best.2. Effects of different fertilized time on the growth of Robinia pseudoacacia and rhizosphere soil enzyme activities after inoculation of AM fungiRobinia pseudoacacia was fertilized nitrogen by 0.4 g/kg on 100 d and 50 d when inoculated G.mosseae, and growth parameters and activities should be determined on 15, 30 and 45 d after fertilization. The results showed that: nitrogen fertilizer increased the mycorrhizal colonization rate, and it increased at 15 -30 d, and then decreased at 30-45 d. After fertilization, the key enzyme activities of carbon-nitrogen metabolism and rhizosphere soil at different stages of the 100 and 50d seedings were significantly increased, and different activities showed different variation with extension of fertilized time, but at each stages, the treatment of AM fungi + N was the highest, while the treatment of neither inoculation nor fertilizer was minimum. the key enzyme activities of carbon-nitrogen metabolism included nitrate reductase (NR), glutamine synthetase (GS), sucrose phosphate synthase (SPS) and sucrose synthase (SS) activitives. Thizosphere soil enzyme activities included urease, invertase, sucrase and catalase activitives. About the seedlings of 100d, influence of AM fungi was stronger, while effect of nitrogen on 50d was stronger.3. Effects of nitrogen and AM fungi on nitrogen absorption and utilization of Robinia pseudoacaciaRobinia pseudoacacia was fertilized nitrogen by 0.4 g/kg on 100d when inoculated G.mosseae, and nitrogen absorption and distribution should be determined on 15, 30 and 45 d after fertilization. The results showed that: Ndff% and the distribution rate of the treatments of inoculated and not-inoculated in each organ of Robinia pseudoacacia shifted as the shift of growth center. 15 d after fertilization, Ndff% and the distribution rate were: stems > leaves > roots, while on 30d and 45 d were: leaves > stems > roots. Inoculation of AM fungi significantly increased the nitrogen utilization of R. pseudoacacia, and reduced the residual rate in the soil, the difference was significant. Under constant nitrogen content free of external nitrogen source, utilization rate, residual rate in soil and nitrogen recovery rate of inoculated gradually declined, while the total loss rate of nitrogen fertilizer gradually increased as time goes on. Utilization rate of not-inoculated gradually increased, but the others were the same with the treatment of inoculated.
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