Shiqin Sun;Xiufeng Ya

College of Life Sciences, Northeast Forestry University, Harbin, P.R. China;College of Life Sciences, Northeast Forestry University, Harbin, P.R. China.

nra;leaves;different positions;rhythm;leaf;camptotheca acuminata seedling

Nitrate reductase activity (NRA) in different plant organs and leaves in different positions of Camptotheca acuminata seedlings was determined by an In vivo assay, the diurnal variation rhythm of NRA in leaves of different positions was observed,and the correlations between leaf NRA, leaf area and lamina mass per unit area (LMA) were also examined. The results showed that NRA in the leaf was significantly highest, compared with that in other organs such as roots, stems and leaves. In this experiment, the 10 leaves were selected from the apex to the base of the seedlings in order. The different NRA occurred obviously in leaves of different positions of C. acuminata seedlings from the apex to the base, and NRA was higher in the 4th-6th leaves.The diurnal change rhythm of leaf NRA showed a one peak curve, and maximum NRA value appeared at about midday (at 12:30 or so). No obvious correlations between NRA and leaf area or lamina mass per unit area were observed. This study offered scientific foundation for the further research on nitrogen metabolism of C. acuminata.