| Setaria italica P.Beauv originated in China and is called millet.It is a self pollinated crop of Gramineae and is known as “the first of small cereals”.Millet itself has strong stress resistance,drought and barren tolerance,and the number of millet genome is small.In recent years,it has gradually become a new generation of model crop.In the process of modern agricultural development,water and nitrogen have become the main factors limiting crop yield and sustainable development.A large number of previous studies have shown that additional and reasonable application of nitrogen fertilizer under water stress can effectively regulate plant reproductive growth and development.Therefore,exploring the reasonable coupling effect of water and nitrogen is conducive to the formation of optimized water and nitrogen regulation measures,which is of great significance to the high-efficiency,high-yield and green development of millet.The effects of water and nitrogen treatment on agronomic traits,yield traits,aboveground dry matter accumulation,root index,grain nutritional quality,antioxidant capacity,osmotic regulation,nitrogen metabolic activity,ABA content,net photosynthetic rate,fluorescence parameters,water use efficiency and nitrogen use efficiency of millet were studied by pot experiment.The results of this thesis are as follows:1.Effects of different water and nitrogen treatments on Millet growth and utilization efficiency of water and nitrogenIn this experiment,there were significant differences in agronomic and yield characters of millet under different water and nitrogen ratios.The spike length,spike diameter,fresh weight per spike,dry weight per spike,grain weight per spike,grain yield,1000 grain weight and yield of millet treated with drought and nitrogen application at seedling stage were the largest;At booting stage,drought without nitrogen application had the lowest related character indexes.Under different treatments,the aboveground dry matter quality of millet showed an increasing trend from heading stage to maturity stage.Drought nitrogen application at seedling stage significantly increased panicle dry weight and decreased leaf dry matter quality;However,drought treatment at booting stage significantly reduced ear dry weight.Under the same water treatment,the root length,root surface area and root volume of nitrogen fertilizer treatment were significantly lower than those of no nitrogen fertilizer treatment.At jointing stage,the root length,root surface area and root volume of drought treatment without nitrogen application at seedling stage were significantly higher than those of control;At heading stage and booting stage,the root length,root surface area and root volume of drought treatment without nitrogen application were significantly higher than those of control.In terms of millet grain quality,water and nitrogen will also have an impact on it.Under the same water stress conditions,the total amount of protein,fat and amino acids in grains under nitrogen application treatment increased significantly,and the contents of other components in grains were significantly different due to different nitrogen application levels and soil water stress degrees.In terms of water and nitrogen use efficiency,the water use efficiency of drought nitrogen application treatment at seedling stage was the highest,and the nitrogen use efficiency of no nitrogen application treatment group was significantly higher than that of other treatments.Under the same water treatment,the water use efficiency of nitrogen application treatment group was significantly higher than that of no nitrogen application treatment,and the nitrogen use efficiency showed the opposite trend.2.Physiological responses of millet to different water and nitrogen treatmentsThe SOD activity,MDA content and pro content of millet treated with drought at seedling stage increased sharply at jointing stage;The SOD activity,MDA content and pro content of millet treated with drought at booting stage increased significantly at heading stage.Under different nitrogen content treatments,the changes of SOD activity and MDA content were not significant,but in drought treatment,no nitrogen application treatment would inhibit the rise of Pro content.Under the same water condition,the NR and GS activities of nitrogen application treatment will increase,and the drought treatment has a certain hysteresis on the improvement of NR and GS activities.Under water stress,the content of ABA in leaves will increase,and the increase range is large under the level of nitrogen application;ABA content in roots also increased,but it increased significantly without nitrogen application.Under the condition of artificial control of light,with the continuous increase of light intensity,the net photosynthetic rate of millet leaves at flowering stage under different water and nitrogen treatments was also increased accordingly.Under the same light intensity treatment,the net photosynthetic rate of millet leaves treated with nitrogen was higher than that without nitrogen.The fluorescence performance of leaves at flowering stage is also quite different.Under water and nitrogen stress,the contents of PHI(Po)and PHI(Eo)will decrease and the content of PHI(Do)will increase.When millet plants were subjected to nitrogen and water stress,the content of PIABS decreased sharply,and the performance index of PIABS with drought and no nitrogen application at booting stage was the lowest.After heading of millet with different water and nitrogen treatments,the SPAD value decreased with the passage of time,and the nitrogen application treatment significantly increased the SPAD value of leaves.The results of this experiment can preliminarily reveal that different water and nitrogen treatments have different responses to the growth,development,physiology and biochemistry of millet.The treatment of drought nitrogen application at seedling stage showed obvious advantages in growth,development,physiology and biochemistry.When millet is planted in the arid and semi-arid area of North China,appropriate drought exercise can be carried out in the seedling stage and appropriate nitrogen application can be increased,which can save irrigation water,maintain crop growth and development and nutrient absorption,and improve the utilization efficiency of water and nitrogen at the same time. |
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