Abstract: A hydroponic experiment was carried out to study the effects of nitrogen (N) supply on the nutritional quality and antioxidative enzyme activities of spinach.The results showed that when the N supply increased from 4 to 8 mmol·L^-1,the biomass of spinach and its leaf vitamin C (Vc) content increased significantly,but a further increase of the N supply induced an obvious decrease of Vc content.An increasing N supply increased the nitrate content in leaves.The soluble oxalate content in leaves decreased slightly with the N supply from 4 to 8 mmol·L^-1 N,but increased with a further increase of supplied N.Total oxalate content increased firstly,and then decreased with increasing N supply.SOD and POD activities increased with the N level up to 8 mmol·L^-1 N,but drastically decreased with increasing N levels.CAT activity decreased when N level elevated.MDA content decreased firstly and then increased with increasing N levels,while free proline content decreased with increasing N supply.All of these indicated that 8 mmol·L^-1 N was an appropriate N supply level for spinach to improve its biomass, nutritional quality,and resistance.

Key words: Urban-rural ecotone, Landscape pattern, Nanjing city