In sugar beet seedling period and sugar accumulation period, the quantity of NR-mRNA raised with the rate of nitrate nitrogen and ammonium nitrogen raised, and the activity of NR raised also, that was the quantity of NR-mRNA of NO3/NH4 —4:0 was the highest. In phyllome formation period and root growth period, the quantity of NR-mRNA of NO3/NH4—3:1 was the highest, and its activity was the highe...