Coupling Effects Of Water And Nitrogen On Source-sink Relationship After Jointing In Millet

In this study,the millet cultivar “Longgu 11” was used as a test material.The pot research was used to study the response to grain yield,biomass,source-sink relationship,non-structural carbohydrate transport,coordination of carbon and nitrogen,water and nitrogen use efficiency of the millet on soil moisture and nitrogen application rate.And then,we want to explore the source-sink relationship and the regulation effect of water and nitrogen in the formation process of millet after jointing by this experiment.The main results are as follows:(1)By setting different treatments of water and nitrogen,we studied the changes of net photosynthetic rate,total leaf area,number of grains per spike and 1000-grain weight in the process of yield formation after millet jointing,and the transport of non-structural carbohydrates.It was found that in the process of yield formation after millet jointing,the restriction effect of the source-sink relationship on the yield of millet is only relative,and the main limiting factors under different environmental conditions are different,and the causes for the limitation are also not the same.Under the conditions of adequate water and nitrogen application after jointing,the main factor that restricts grain yield is the grain library.The main reason for the limitation caused by the appropriate amount of nitrogen application is that the utilization of the non-structural carbohydrates temporarily stored by the kernels in the plants is not sufficient.That is,the ability of the reservoir to store and transform photosynthetic products limits the further increase of the millet yield.The main reason for the limitation caused by excessive nitrogen application is that the number of sinks.That is,the shortage of grains per ear limits the increase in millet yield.Under normal moisture and nitrogen application after jointing,the source is the main factor that restricts the yield of millet.The main reason for the limitation is that the assimilate produced by photosynthesis in the later growth stage cannot meet the demand of the grain bank,resulting in a lower grain weight and thus affecting the grain weight.Under water stress and no nitrogen application after jointing,the source;library limits the yield of millet,and the library is the main limiting factor.The main reason for the limitation was that the non-structural carbohydrates of the plants with weak photosynthetic capacity and transported from the vegetative organs to the grain accumulated in the stem stalk and did not enter into the grain.(2)By setting up different water and nitrogen treatments,we studied the changes in grain yield,biomass,grain coefficient,harvest index,and water and nitrogen use efficiency.The main results are as follows: Appropriate water conditions and reasonable application of nitrogen fertilizer ensure that the high yield of millet,water stress and excessive application of nitrogen fertilizer are not conducive to the increase of millet yield,biomass,and water and nitrogen use efficiency.The suitable water and nitrogen conditions are to increase the grain yield by increasing the overall biomass of the millet plant and increasing the transportation and distribution to the grain.(3)By setting up different treatments of water and nitrogen,we studied the changes in the degree of coordination of carbon and nitrogen during grain yield after jointing with millet.The main results are as follows: The ratio of carbon to nitrogen in the top three leaves of millet showed a significant negative correlation with the net photosynthetic rate.Under the suitable conditions of water and nitrogen fertilizers,the carbon and nitrogen metabolism in the upper three leaves are relatively coordinated,so that the net photosynthetic rate is maintained at a higher level,and the source supply of plants is increased.However,the carbon and nitrogen ratio of stems increased under this environmental condition and was negatively correlated with the non-structural carbohydrate transport rate of the vegetative organs.Therefore,we speculate that,under appropriate moisture and reasonable nitrogen application conditions,the ability of the grain(library)to receive,transform and store photosynthetic products is the main factor restricting the further increase of grain yield.