Differences Of Photosynthetic Characteristics And Key Enzymes Activity Involved In Nitrogen Metabolism In Eggplant Genotypes With Different Nitrogen Use Efficiency

The aim of this study is to investigate the differences of the photosynthetic characteristics and key enzymes activity involved in nitrogen metabolism in the eggplant genotypes with different nitrogen use efficiency. Three nitrogen efficiency genotypes of eggplant were used to study the nitrogen metabolism by testing the photosynthetic rate, chlorophyll content, nitrate reductase (NR) activity, glutamine synthetase (GS) activity, and other indexes. This experiment was conducted by using the solution and field culture under the normal nitrogen supply and low nitrogen stress. On the other hand, the differences in biomass of the nitrogen efficiency genotypes of eggplant under different nitrogen supply were studied by using the solution culture. The results as follows:1. Using the solution culture under the normal nitrogen supply, all the photosynthetic indexes of nitrogen efficiency genotypes were decreased first then increased starting from the fifth to the fifteenth day after the fifth leaves outspreaded, while they displayed a tendercy of decreasing after the fifteenth day. Using the solution culture under the low nitrogen stress, all the photosynthetic indexes of nitrogen efficiency genotypes were increased starting from the fifth to the fifteenth day after the fifth leaves outspreaded, the indexes were the highest on the fifteenth day,while they were decreased from the fifteenth to the twenty-fifth day. The genotype 07-862 had stronger photosynthetic ability compared with other two genotypes 07-857 and 07-860 . Most of the photosynthetic indexes between the nitrogen efficiency genotypes had significant differences.2. Using the field culture under the low nitrogen stress, all the photosynthetic indexes of nitrogen efficiency genotypes displayed a tendercy of increasing from the eighth to the twenty-forth day after the fifth leaves outspreaded. The indexes were the highest on the twenty-forth day, while they decreased from the twenty-forth to the fortith day. The genotype 07-862 had stronger photosynthetic ability compared with other two genotypes 07-857 and 07-860. Most of the photosynthetic indexes between the nitrogen efficiency genotypes had significant differences.3. This experiment was conducted by using the field culture under the normal nitrogen supply and low nitrogen stress. After the fifth leaves outspreaded, the change tendercy of enzymes activity involved in nitrogen metabolism of nitrogen efficiency genotypes was the same with the tendercy using the field culture. Compared with other two genotypes 07-857 and 07-860, 07-862 had stronger enzymes activity involved in nitrogen metabolism. The enzymes activity involved in nitrogen metabolism between the nitrogen efficiency genotypes had significant differences.4. The correlation coefficient of photosynthetic indexes between solution and field culture under the normal nitrogen supply was low and not significant. However, a strong correlation of the indexes bewteen solution and field experiments under the low nitrogen stress was observed. The photosynthetic indexes of eggplant genotypes under the field culture can be predicted by using the solution culture under the low nitrogen stress. This will be the basis to screen the nitrogen efficiency genotypes of eggplant during early stage.5. Using the solution culture, we found the differences in biomass under different nitrogen supply. The results showed that plant height, number of leaves, leaf area, and root biomass of the nitrogen efficiency genotypes were decreased as the nitrogen level was reduced. Compared with other two genotypes 07-857 and 07-860, 07-862 had stronger endurance ability to the low nitrogen stress. Under the low nitrogen stress, the differences in nitrogen uptake efficiency for the three genotypes were due to the differences in root characteristics. The differences in nitrogen uptake efficiency were the main reason to differences in nitrogen use efficiency in different genotypes under the normal nitrogen and low nitrogen stress.