Effects Of Nitrogen Granular Fertilizer On Rice Grain Filling And Quality Under Open Warming Conditions

Rice is one of the most important food crops for human beings,and most of the population in China feeds on rice.Rice is an important source of human carbohydrates.According to the report issued by the Intergovernmental Panel on Climate Change(IPCC)in 2013,comprehensive observations and key indicators of the climate system indicate that the trend of global climate change is still on the rise,and that the frequency of extreme weather events is on the rise in addition to the continued rise in global temperature.By the end of this century,the global average temperature is expected to rise by 2-4 degrees Celsius.Many studies have shown that grain filling stage is the most important period in rice growth and development.Excessive temperature during grain filling stage will bring about adverse effects such as yield reduction and quality decline.And the amount of nitrogen fertilizer and the way of fertilization have a significant impact on the formation of rice yield and quality.Scientific and rational application of nitrogen fertilizer can not only improve the nitrogen conversion rate and yield of rice,but also help to improve the quality of rice.Understanding the changes of gene expression of key enzymes in starch synthesis in rice grains under different nitrogen application treatments can better coordinate the relationship among fertilizer utilization,yield and quality.In this experiment,Wuyunjing No.24 was used as material,and the open heating system of FATE(Free-air Temperature Enhancement)was used.Four treatments were set up by increasing the application of nitrogen granular fertilizer:no application of nitrogen fertilizer(CK),no application of nitrogen fertilizer(ET),no application of nitrogen fertilizer(CKN)at room temperature,and warming application of nitrogen fertilizer(ETN).The effects of nitrogen on quality characteristics,yield formation and key enzymes of starch synthesis of rice under open heating were studied.The main results are as follows:1.Appearance quality deteriorated,chalkiness rate and chalkiness area increased,and roughness,milled rice rate and head rice rate decreased in rice processing quality.Temperature increased the accumulation of albumin,globulin and glutenin,but the content of gliadin decreased.The peak viscosity and thermal slurry viscosity were increased significantly,and the reduction value and gelatinization temperature were decreased significantly.2.Temperature and nitrogen fertilizer had significant effects on grain filling and yield components.Under warming conditions,the grain filling rate is faster in the early stage and slower in the late stage,which leads to the lack of filling stamina,and significantly reduces the seed setting rate and 1000-grain weight,thus leading to a decrease in yield.Increasing N fertilizer application decreased the initial growth potential,prolonged the active filling period,decreased the filling rate and reduced the starch synthesis rate.Nitrogen granular fertilizer is beneficial to improve the phenomena of excessive grain filling rate and reduce amylose content under field warming,and to alleviate the efficiency of yield decline.3.The expression of key enzymes related to starch synthesis in grains 5 days after anthesis was significantly increased under open warming conditions.The expression of key enzymes related to starch synthesis in grains at 15 days after anthesis was significantly reduced.Nitrogen application had a certain mitigation effect,which increased amylose synthesis and decreased amylopectin synthesis in rice grains under warming conditions,and alleviated the decline of rice yield and quality under warming conditions.