Low Grain Plumpness Of Coix Seed And Its Response To Combined Application Of Nitrogen,phosphorus And Potassium

There are great differences in the opening of spikelets and the order of seed setting in different parts of Coix.Generally,the spikelets bloom late,the seed setting rate is low and the plumpness is low.In order to clarify the low plumpness of Coix seeds and its response to the combined application of nitrogen,phosphorus and potassium,this experiment will be conducted in Xingren City,Guizhou Province in 2021.Guiyi.1 and Shizong Heike were used as materials,By studying the differences in grain carbohydrate content,starch synthesis-related enzyme activities,grain filling rate,seed setting rate,filling degree and grain weight in different parts,the grains in different parts of Coix were studied at the same time.The response of weight,seed setting rate and fullness to the combined application of nitrogen,phosphorus and potassium fertilizers.The purpose is to preliminarily find out the low grain fullness of different parts of Coix and its physiological basis,and to promote the grain filling of weak grains through fertilization regulation,and to determine the best way to reduce the low grain fullness.The ratio of nitrogen,phosphorus and potassium provides the basis and guidance for reasonable fertilization and high-yield and high-quality cultivation of Coix.The main findings are as follows:1.The growth of grain dry matter in different parts of Coix is in line with the"S"-shaped growth curve,that is,with the grain filling process,the grain dry matter growth shows a dynamic change of"slow-fast-slow",and the overall performance is the increase of grain dry matter after flowering.During the whole grain filling stage,the dry weight of grains in different parts of the Coix showed the order of“Lower1>Upper>Middle>Lower 2>Lower 3”.The grain moisture content of each part of the Coix showed a decreasing trend with the filling process,and the moisture content（y）had a very significant linear relationship with the days after flowering（d）.The grain moisture content of the Coix was the highest on the7th day after flowering,ranging from 65.44%to 77.44%,and the grain water content of the two varieties on the 49th day after flowering was the lowest,ranging from 23.78%to 30.15%.2.The grain filling rates of different parts of Coix were first increased and then decreased with the days after flowering.Among them,the grain filling rate of Guiyi.1 reached the maximum on the 28th day after flowering,while Shizong Heike reached the maximum on the 35th day after flowering.Comparing the average grain filling rate（V_a）of each part of the grain,it was found that the“Lower 1”parts was the largest at 1.2 mg/d,which was higher than that of the“Lower 2”parts（1.05 mg/d）and the“Lower 3”parts（1.02mg/d）,respectively,15.2%and 17.4%;the maximum grain filling rate(V_max)of each part of the grain is also the highest in the lower part,which is 2.04 mg/d,which is higher than that in the“lower 2”parts（1.81mg/d）and the“lower 3”parts（1.79 mg/d）,respectively,12.7%and 13.9%.The seed setting rate of different parts of Coix seed is“Lower 1>Middle>Upper>Lower 2>Lower3”,among which the seed setting rate of the“Lower 1”part is 77.50%,which is higher than that of the“Lower 2”parts（73.36%）and the“Lower 3”parts（72.49%）,respectively,5.6%and 6.9%;the grain filling degree of different parts is“Lower 1>Upper>Middle>Lower 2>Lower 3”,and the grain filling degree of“Lower 1”part（80.21%）is significantly higher than that of“Lower 2”parts（73.46%）and“Lower3”parts（72.40%）,which were 9.1%and 10.8%higher respectively;the single-grain weight of different parts showed the order of“Lower 1>Upper>Middle>Lower 2>Lower 3”,The single grain weight of the“Lower 1”part was 83.67g,which was 12.8%and 14.67%higher than that of the lower part 2（74.15g）and the lower part 3（72.96g）,respectively.3.The grain starch accumulation in different parts of Coix is in line with the"S"-shaped growth curve.The grain starch content of each part is in the mature stage,and the performance of each part is“Lower 1>Upper>Middle>Lower 2>Lower 3”.Among them,the“Lower 1”part of the grain starch content（39.12%）were 12.3%and 16.4%higher than the“Lower 2”parts（34.83%）and the“Lower 3”parts（33.61%）,respectively,and the order of grain starch content in each part was basically consistent with the trend of grain dry matter accumulation.The maximum accumulation rate of starch showed as“Lower 1>Upper>Middle>Lower 2>Lower 3”,among which the starch accumulation rate of the“Lower 1”part was 0.35 mg/d,and the“Lower 2”and the“Lower 3”parts were 0.19 mg/d and 0.21 mg/d,respectively.There was a very significant positive correlation between grain weight and starch content,and both grain starch accumulation rate and grain filling rate were extremely significantly positively correlated.4.The activities of Sucrose Synthase（SS）,Sucrose Phosphate Synthase（SPS）,Starch Debranching Enzyme（DBE）and Starch Branching Enzyme（SBE）in different parts of Coix seed increased first and then decreased with the grain filling process.Among them,among the SS and SPS activities of grains in various parts,the enzyme activities of the lower three parts were higher than those of the upper part and the middle part of the grain in the early and middle stages of grain filling.The content of grain enzyme activity in the upper part and the lower part 1 was higher than that in other parts,and the enzyme activity of each part decreased as a whole in the later stage of grain filling.5.Judging from the response of different parts of grain filling difference to fertilizer application,The treatment 9（N₂P₂K₁）significantly improved the average grain filling rate and maximum grain filling rate of the“Lower 2”parts and the“Lower 3”parts compared with the average value of the corresponding parts of other treatments.The average grain filling rate and the maximum grain filling rate of the“Lower 2”parts increased by 11.7%and 10.7%,respectively;the“Lower 3”parts increased by 16.1%and 16.4%,respectively.Compared with the average value of the corresponding parts of other treatments,The treatment 9 can significantly improve the yield traits such as the seed setting rate and filling degree of the“Lower 2”parts and the“Lower 3”parts of Coix,and the seed setting rate of the“Lower 2”parts and the“Lower 3”parts increased by 3.8%and 11.1%,respectively.the grain filling degree increased by 10.9%and 22.3%,the thousand-grain weight increased by 7.35%and 14.4%,and the total grain weight increased by 31.1%and22.9%,respectively.To sum up,the average grain filling rate,maximum grain filling rate,grain setting rate,grain filling degree and starch content of the“Lower 2”parts and the“Lower 3”parts were lower than other parts,and the“Lower 1”parts was higher than other parts,which preliminarily showed that the“Lower 2”parts and the“Lower 3”parts were the weak granules of Coix,and the“Lower 1”part was the strong granules of Coix.In the response of grain filling difference of different parts of Coix seed to NPK combined application,the treatment 9 level can effectively improve the seed setting rate,filling degree and thousand-grain weight of inferior grains（Lower 2 parts and Lower 3 parts）of Coix,thereby increasing the yield of Coix.