Abstract: The growth and the accumulation prosess of dry matter of the Chinese Pine's and Chinese Arborvitae's containerized-seedlings under the plastic greenhouse condition which not being controlled are studied in this paper and compared with those (seedling) grown under the field condition. The main results obtained as following:1. The biomass of the containerized-seedling under the condition of the plastic greenhouse are lower than those under the fiold condition, the difference between the two conditions is highly significant.2. The overwintering survival rate of the seedlings in the plastic greenhouse shows also a relatively lower percentage compared with those under the field conditions.3. The difference of the net assimilation rate among the three treatments in both species is extremely significant, the highest net assimilation of Chinese Pine's seedlings appeared in May and June, while that of the Chinese Arborvitae seedlings appeared in July and August.4. The major factor which influences the net assimilation rate is the high temperature.

Key words: Chinese Pine, Chinese Arborvitae, Plastic Greenhouse, Containerised-Seedlings, Net assimilation