Abstract: The effects of different nitrogen forms on root respiratory metabolism and on biomass in seedlings of Cerasus sachalinensis Kom. were investigated. The results showed that，with a same amount of nitrogen application，the application of nitrate nitrogen and amidonitrogen significantly enhanced root activity and accumulation of respiratory substrates during the whole experimental period（28 d），while the application of ammonium nitrogen only enhanced the root activity and the accumulation of respiratory substrates during the 14 days after the application. Whereafter，the root activity and respiratory substrate content significantly decreased. Application of nitrate nitrogen enhanced the activities of key enzymes in tricarboxylic acid（TCA）cycle，increased the ratio of TCA cycle to the total respiratory pathway by 30.4% compared to that in the control and increased the content of pyruvic acid and citric acid the intermediates of respiratory metabolism. Whereas，the pentose phosphate pathway（PPP）and the alternative oxidase（AOX）pathway were decreased by 35.0% and 32.7% respectively at the same time. The application of ammonium nitrogen had opposite effect to the application of nitrate nitrogen on activities of key enzymes in TCA cycle，on TCA cycle，intermediates of respiratory metabolism，PPP and AOX pathways. Application of amidonitrogen had similar effects to the application of nitrate nitrogen except having no obvious effect on activates of key enzyme in glycolysis pathway（EMP）and in respiratory electron transport. The application of the three different types of nitrogen improved the growth of the seedlings. The enhancement of biomass by the application of the 3 types of nitrogen was nitrate nitrogen > amidonitrogen > ammonium nitrogen > control.

Key words: Cerasus sachalinensis Kom., nitrogen, respiration, biomass