| In recent years, with the increasing of potato acreage year by year, people have become increasingly aware of the importance of potato in agricultural production, and reasonable fertilization has important significance for the production of potato, nitrogen fertilizer is one of the most important fertilizers, the reasonable supply and efficient use of it is an important guarantee for high and stable yield and quality of potato. This experiment selected different ripe stage of two fresh food potato varieties, determination the morphology and photosynthetic indexes,dynamic changes of nitrogen metabolism key enzyme activity, nitrogen uptake utilization, yield and quality index, analyze the relationship between nitrogen metabolism enzymes and nitrogen utilization, study the effects of nitrogen application rate on yield and quality under different nitrogen application levels. The main results are as follows:(1)The height, main stem number and stem diameter of plant were increased with the increasing of nitrogen rate, and the differences between treatments are significant; net photosynthetic rate of two varieties showed a single peak curve, maximum value occurs in the flowering period, the net photosynthetic rate of leaves could be improved by applying nitrogen fertilizer, the net photosynthetic rate of Dongnong 311 reached maximum value under the condition of 200 kg/hm2 nitrogen application rate and Dongnong 312 reached the maximum at 150kg/hm2; SPAD value decreased gradually with the growth of potato; leaf area of two varieties reached the maximum in early tuber bulking stage, in the same growth period, leaf area under high nitrogen treatment was significantly higher than that of low nitrogen treatment, comprehensive comparison, when the amount of nitrogen fertilizer was 150, the above indexes showed the best overall performance.(2)The four key enzyme activities of nitrogen metabolism were significantly or extremely significantly positively correlated with the amount of nitrogen application, and the enzymes activities of Dongnong 312 were higher than those in Dongnong 311. The trend of NRA in the whole growth period showed a double peak curve, the peak appeared at the seedling stage and tuber enlargement stage, but the second peak is less than the first; The trend of Ni RA consistent with NRA in the whole growth period, but the activity of Ni R lags behind a period of NR; GS activity showed a double peak curve, the first peak appeared at seedling stage, the second peak ofDongnong 311 appears in tuber bulking period and Dongnong 312 appears in the tuber enlargement period, and the second peak was lower than the first; GOGAT activity showed a single peak curve changes, the activity peak of Dongnong 311 appears in the tuber expansion period, Dongnong 312 appears in the tuber bulking stage.(3)The nitrogen content of potato leaf decreased gradually with the growth period of time, but in the same growth period, leaf nitrogen content increased with the nitrogen increasing; while the whole plant nitrogen accumulation showed a single peak curve, and the peak appears at starch accumulation stage, in the same growth period, nitrogen accumulation increaseing with the amount of nitrogen increasing; nitrogen absorption rate showed the trend of slow-fast-slow, and reached the maximum value in the tuber enlargement stage, in a certain range, increasing the amount of nitrogen fertilizer can significantly improve nitrogen absorption rate, but high nitrogen rate on nitrogen absorption rate has not improved significantly; at the same time, the high nitrogen treatment can significantly improve the total accumulation of plants, but it is not conducive to the effective use of nitrogen fertilizer, when the amount of nitrogen application was 50 kg/hm2, the nitrogen utilization efficiency was the highest.(4)The starch and vitamin C content decreased with the nitrogen fertilizer increasing, but crude protein and reducing sugar content increased with the nitrogen fertilizer increasing,generally speaking, high nitrogen treatment was not good for the formation of the fine quality of tubers; Tuber dry matter content was gradually increase as “S†type curve in the whole growth period, and increased with nitrogen fertilizer increasing; the trend of yield showed parabolic curve with the nitrogen fertilizer increasing, the yield and its components were maximum at 200 kg/hm2 in the amount of nitrogen application and the optimum N rate of Dongnong 311 was 176 kg/hm2,Dongnong 312 was 174 kg/hm2.(5)There was significant correlation between the four kinds of nitrogen metabolism enzyme activity with nitrogen utilization characteristics and yield, the activity of GS and GOGAT could be used as an indicator to determine the difference of plant N accumulation, the enzyme activity at early tuber bulking stage to late tuber bulking stage can be used as a comprehensive evaluation of yield and indexes of nitrogen utilization rate. |
