Study on the Relationship between Nitrate Reductase Activity, Nitrogen Storage Contents and the Growth of Chinese Fir

This paper deals with nitrate reductase (NR) activity and nitrogen storage contents (nitrate,amino acid and total nitrogen) in seedlings of Chinese Fir (Cunninghamia lanceolata Hook.) with different growing rates. The results showed that (1)the level of NR activity varied with the growing period. Generally, during the initial growing stage NR activity was low, and the maximum activity was observed at the peak of the growing season. The NR activity in seedlings of the fast growing clone was higher than that in the slow growing clone. NR activity in young seedlings of different age (1,2,3,4,5 years old) was higher in the fast growing clone than that in the slow growing clone. Positive relationship between NR activity in seedling (1-year old) and tree height (5-year-old) was observed. (2) the fast growing clone had higher ability of uptake and assimilation of nitrogen than that of the slow growing clone. Thus, during and after growing stage, the former contained higher contents of nitrate, amino acid and total nitrogen than the later did. Glutamic acid, aspartic acid and histidine contents in leaves and phloem are about 70% of the total amino acid contents.