| For the clarifying the effect of pertinence between the CO2 concentration double or temperature elevating in different nitrogen contents on plant, three-year-old seedlings of two conifer species Picea koraiensis Nakai and Picea meyeri Rehd.et Wils were studied by the portable photosynthetic analysis system Li-6400.The index of photosynthesis including photosynthetic rate, respiration rate and water using efficiency in ambient CO2 concentration and normal temperature were compared with the condition of CO2 concentration double or temperature elevating 4C in different nitrogen lever treatments. The related index of the chlorophyll variation and biomass were analyzed simultaneously. The results as following:1 . Under double concentration of CO2 condition, the maximum net photosynthetic rate of all Picea koraiensis groups increased, and in the group of Picea meyeri with high nitrogen supplying increased at July, and appeared lower at June and August; The maximum net photosynthetic rate of low nitrogen treatment group decreased from June to August. It was different between the two species in responding to the change of concentration of CO2.2. The two species had different response to nitrogen supplying. The adaptation to nitrogen had an effect on photosynthesis response to double concentration of CO2 of Picea meyeri. High nitrogen can not induce photosynthetic adaptation on seedling, otherwise, low nitrogen can induce it in Picea koraiensis; but photosynthetic adaptation was observed in both low and high nitrogen conditions in Picea meyeri, It indicated that Picea meyeri was more sensitive to nitrogen condition than Picea koraiensis.3. During the growing season from June to August, elevated 4C simulating condition did harm to the growth of the two species, resulting in the lower maximum net photosynthetic rate than the control condition. Sufficient nitrogen supplying could alleviate the stress of high temperature. The maximum net photosynthetic rate was higher than that of group with low nitrogen under high temperature.4. Content of chlorophyll affected the photosynthesis and the product of photosynthesis. The a/b ratio of chlorophyll increased under double concentration of CO2 , which indicated that it was helpful for forming chlorophyll a. Proper temperature enhanced the chlorophyll synthesize, so photosynthesis ability increased. The temperature became a stress factor when it exceeded the limited growth temperature which can restrict the growth.5. The study showed that under the double CO2 concentration, sufficient nitrogen, and no other condition stress, the ratio between root and crown can not be affected by elevated CO2 concentration. The ratio between root and crown increased at insufficient nitrogen. Under different condition, the biomass of underground parts in low nitrogen was higher than that of groups in high nitrogen supplying. It indicated that the two species seedling adapted to insufficient nutrition by increasing the biomass of root systems.6. Nitrogen was one of the most important nutrition elements for plant growth, as a result, more nitrogen should be used at elevated CO2 and adjusting the proportion of C/N ratio in order to increase the growth and production of plant.7. Chloroplast was very important for plant photosynthesis, the result of transmission electro microscope observation showed that the number of chloroplast increased under elevated CO2, and leading to increasing of the photosynthesis rate; but long-term CO2 enrichment was harmful to plant growth, which made photosynthesis decreasing, because excessive starch accumulation limited the photosynthesis in the chloroplast probably.
|
PDF Full Text Request