EFFECT OF DIFFERENT LEVELS OF NITROGEN FERTILIZER ON NITRATE REDUCTASE ACTIVITY IN LEAVES OF CUNNINGHAMIA LANCEOLATA WITH DIFFERENT GROWTH RATES

Nitrate reductase activity (NRA),chlorophyll,protein,free amino acid and nitrate contents of different clones of Cunniughamia lanceclata were determined in relation to nitrogen fertilizer.Nitrogen was supplied as NH4NO3.There were differences of (NRA) between the fast growing and slow growing clone seedlings.The former exhibited higher NRA.They were 8-10 μmol NO2-/30 min/g fresh weight but the latter was 6.2 μmol NO2/30 min/g fresh weight.NRA in seedling leaves increased with the increase of nitrogen fertilizer.While the concentration of nitrogen fertilizer was higher than 350 mgN/L,NRA decreased.But NRA in fast growing clone seedlings were higher than those in slow growing clone seedlings.They had NRA values of 10-12 and about 7.1 μmol NO2-/30 min/g fresh weight,respectively.