| Researched on effecting of grain plumpness of rice and physiological activities of grains under the different panicle nitrogen fertilizer levels will provide important information for inferior grains of large panicle rice varieties with heavier grain weight. In the present study, Japonica rice, Yujing 6 ,is a typical asynchronous type with lighter inferior grain weight. Three levels of panicle nitrogen fertilizer were applied (N0:0kg/ha; N90:90kg/ha; N180:180 kg/ha) at young panicle differentiation stage for studying grain plumpness respectively from dry matter accumulation, the dynamic change of sap flow , grain sink and so on. By field experiments, the study on mechanism of inferior grain plumpness under panicle nitrogen regulation was carried out on experiments farm of Henan Agricultural University from 2006 to 2009. The results were as follow:1 The effect of nitrogen fertilizer on the yield components was studied. The results showed that the yield of N90 was highest, secondly was N0 treatment, and the lowest was N180 treatment. The effects of nitrogen fertilizer on the yield conponents were meanly shows on ear characters. For yujing6, the 1000-grain weight and inferior grain plumpness were caused by different yield between treatments. The more the spike nitrogen fertilizer application, the lower the 1000-grain weight and inferior grain plumpness.Three spike nitrogen fertilizer levels had effects on inferior grain rice quality significantly. The lower nitrogen fertilizer had improved milled quality significantly or extremely significantly. And the spike nitrogen fertilizer had effects on chalky percentage, chalky area and chalkiness of three treatment, specially on chalky percentage, having an significantly or extremely significantly differences at three treatment. That is to say rice quality of inferior grains will get worse with spike nitrogen fertilizer application rising, but had lower influences on superior grains.2 At grain filling stage, the effects of nitrogen application on the clover leaf chlorophyll content was different, more nitrogen applied, higher SPAD values, at the entire grain-filling stage the SPAD value of N0 treatment was significantly lower than N90 and N180 treatment, at the same time the SPAD value of N0 treatment declined fastest, most yellow leaves, especially at the late grain filling stage, that shows no nitrogen applied were lead to the phenomenon of premature aging.3 The effects of nitrogen applied on the rice after flowering non-structural carbohydrate accumulation and output, results showed that the whole grain filling stage, the three treatments were reflected in similar trends on the changes of stem and sheath of sugar and starch content, at the early grain filling stage ,the content was the highest, the soluble sugar and starch content of stem at 5-22 days after anthesis decreased faster .However, the soluble sugar and starch content of sheath in 5-15 days after anthesis decreased faster ,during the remaining grain filling stage, the soluble sugar and starch content of stem and sheath between three treatments were lower and changes in the lower flat, soluble sugar and starch content of stem and sheath between three treatments at 43 days after anthesis had a certain recovery ,and at the late grain filling stage sugar and starch content of N0 treatment accumulated most. Third, stem and sheath to deal with that sugar and starch content in the changing trend. It shows that the differences in sugar and starch content between three treatments were only at different content and mainly concentrated in the early and middle stage of the top two or top three on the stem and sheath.In output rate of non-structural carbohydrates in stem and sheath, N0 treatment only had the highest output rate of sugar content in the sheath, but it had the smallest output rate of sugar and starch content in stem and sheath, and this had correlated with N0 treatment having a more recovery with the soluble sugar and starch in the stem and sheath. The output rate of N90 and N180 treatments was higher than N0 treatment, and the difference of the output rate between N90 and N180 treatment in stems. The ratio of sugar to flowers sheath of sugar between three treatments had manifested as more nitrogen applied with the lower the ratio of sugar to flowers. The ratio of sugar to flowers in stem and sheath at heading had a very significant positive correlation with 1000-grains weight and grain plumpness.The daily changes of sugar and starch content in stem and sheath during grain filling stage had not the same trends. The rising or decreasing range of the sugar content in N0 treatment in daily changes was more than N90 and N180 treatment, especially the declining range. In the early and middle grain filling stage the higher soluble sugar and starch content of stem and sheath , and the more range within which the sugar and starch content increased or declined larger, particularly the rapid declined, was favor to grain plumpness.The size of daily output was N0> N90> N180 treatment at grain filling stage, The output in N0 treatment of soluble sugar was relatively large, whereas the N90 and N180 treatment of starch content had the larger daily output than the daily output of sugar content, and the entire grain filling stage , the output of stem and sheath to the top two or top three on the stem and sheath were more output. The output of three treatments at the early and middle grain filling stage occupied by the most output at whole grain filling stage,. N90 and N180 treatments had a smaller output at the late grain filling stage. N90 and N180 and N0 to deal with The differences in output between N0 treatment and N90 and N180 treatment mainly concentrated in the early and middle stage, while the differences between N90 treatment and N180 treatment in output mainly in the 10, 22 ,35 days after anthesis. The daily output in stem and sheath of sugar and starch content had a positive correlation with 1000-grain weight of superior and inferior, at 29-43 days after anthesis mostly negative correlation, but mostly not related significantly.4 At grain filling stage, the base sap flow strength for the downward trend, and sap flow of N90 and N180 treatments in the middle grain filling stage declined more, and N0 treatment, at early and middle grain filling stage sap flow declined in more slowly, while at late grain filling stage sap flow dropped more than N90 and N180 treatments. Ear during the day ,the sap flow of N0 treatment had a little lower than N90 and N180 treatment, at the late grain filling stage the sap flow was significantly lower than that to deal with N90 and N180. at night, the sap flow of N0 treatment at the whole grain-filling stage was significantly more than N90 and N180 treatments. Sap flow per grain of three treatment, with the exception at the late grain filling stage the smaller sap flow, at the early and middle grain filling stage during the day and during the night-time at the whole grain filling stage, the sap flow per grain of N0 treatment were larger than the N90 and N180 treatment, at the early grain filling stage during the whole day and at the middle and late grain filling stage at night per grain the sap flow had a significant positive correlation with grain plumpness.5 The effects of nitrogen applied on grain weight and grain plumpness, grain weight and grain plumpness of inferior grains showed an increase in nitrogen application rate with the reduction. Grain weight and grain plumpness in different positions at grain maturity was closely related to the order spikelet flowering sooner or later, primary branches, grain weight and plumpness in different positions performed , 6> 5> 4> 3> 2; secondary branches ,the branches 1> branches 2> branches 3> branches 4, 2 branches on each bit of the tablets for 1> 4> 3> 2, the average grain weight and grain plumpness on primary branches were greater than grain weight and plumpness on the secondary branches, and the differences with the increase in nitrogen application increased. The differences of grains at different positions between grains weight and grain plumpness of superior grains was less, but inferior grains was bigger. Those grains on secondary had more differences than that on primary branches, The differences between three treatment come from secondary branches exception of grain 1, and followed by grain 2,3 of primary branches. In weak positions of inferior grains were the most sensitive to nitrogen regulation.At grain filling stage, the average changes of grain dry weight of superior and inferior grains were "S"-type. Superior grains had the rapid weight gain to 25 days after anthesis, followed by the grain had been basically full irrigation. The dry weight of N0 treatment only slightly higher than the N90 and N180 treatment at the beginning grain filling stage, in 15-25 days time grain weight increased significantly faster than the N90 and N180 treatment. The grain weight of superior grains of N90 and N180 treatments had a similar increasing trend, no significant differences. Grain weight of inferior grains increased slowly before the early and middle grain filling stage, Grain weight of N0 treatment since the beginning grain filling stage was faster than N90 and the N180 treatment, in 5-20 days after anthesis grain filling rate of N0 treatment was slightly faster than the N90 and N180 treatment, grain-filling rate of N0 treatment was significantly higher than N90 and N180 treatment at 20-25 days after anthesis. the differences of grain filling rate of N90 and N180 treatment at 20 days after anthesis.At grain filling stage, the grain filling rate of the average grain weight of superior or inferior grains, are faster at night than at the day. During the day, grain filling rate of the 7:00-13:00 time was greater than 13:00-19:00, at night, the grain filling rate of the 19:00-1: 00 time was faster than in the 1:00-7:00 time. At the same grain filling, daily changes of grain weight between treatments or superior and inferior grains basically the same trend. The daily increasing grain weight of superior grains was larger at early and middle grain filling stage. Parts of superior grains weight in the 1:00-7:00 time had decreased at late grain filling stage. The time points at which the grain filling rate of N0 treatment was larger than the N90 and N180 treatments was at the time of day there, and the larger the difference in the daytime.The grain filling order of superior or inferior grains in weak positions was same as the order of flowering, as early as the early grain filling, grain weight and flower order. Grain filling capacity of primary branches was stronger than the secondary branches on the disadvantaged position of the grain-filling ability, and its rapid filling rate and filling time beginning earlier than two branches. Weak grains of inferior grains on primary or secondary branches, respectively,at 15,20 days after the beginning of large grain-filling rate,N0 grain weight of N0 treatment on primary branches increased significantly faster than the N90 and N180 treatment at 20-25 days after anthesis, at this time N90 and N180 treatment had a sluggish period. Second, the branches, the grain-filling rate of N90 and N180 treatments in 25-35 days after flowering was significantly less than N0 treatment. To maturity, grain weight of N0 treatment was greater than N90 and N180 treatment. Weak grains of inferior grains had a same trend as superior grains. The differences of grain filling rate between three treatments were usually larger in the daytime and two time points in the daytime are great.6 The spike nitrogen fertilizer had an effect on grain sugar content. The sugar content of grain 1 in primary branches was not the lowest ,but was grain 6.The sugar content of different grains on primary branches was 6<1<5<4<3<2,was different the order of grain filling. Inspiting of superior or inferior grains, the difference of sugar content of different grains in primary branches at N0 and N90 treatment was greater, and the difference of sugar content of different grains at N180 treatment in primary branches was lower. The average sugar content of all superior grains at primary branches of get greater with spike nitrogen fertilizer application rising, but had lower differences on inferior grains. On secondary branches ,generally, grain 2 had the highest sugar content, and the sugar content of the different positions grains had lower differences .The differences of sugar content of superior grains in primary branches at three treatments was lower, presented as the more the nitrogen fertilizer applied, the lower the sugar content of grains at secondary branches. In inferior grains, the higher of the average sugar content of all secondary grains was N0 and N180 treatment, and the average sugar content of N90 treatment was lower. At early grain filling stage ,the sugar content of grains decreased rapidly. At middle grain filling stage, the sugar of grains had a certain amount rising .At late grain filling stage, the sugar content and its changes were lower .At 15 and 20 days after flowering(DAF) ,the dynamic changes of three treatments were same , the differences of three treatment and the daily changes were lower. At 10 and 25-35 DAF ,the daily changes of three treatments and the differences of sugar content at three treatment were greater. And the differences of sugar content didn't showed obviously at the different grain plumpness treatment.7 Grain maturity bit different grain amylose content changes, amylose content of superior grains on average slightly higher than the inferior grains. Between grains of higher or lower starch content and flowering sooner or later, the order was not consistent. The differences of grains sugar content on secondary branches were more than primary branches, especially the grain 2 on the secondary branches, and the average sugar content on the primary branches was higher than grains sugar content on the secondary branches. Compared with superior grains, the difference of inferior grains at different positions, and grain 4 of inferior grains at primary branches had the lowest amylose content. Among treatments, regardless of superior or inferior grains, the average amylose content increased with the nitrogen reduction to deal with the difference between primary branches and secondary branches with the amount of nitrogen increases.The differences amylopectin content of inferior grains at different positions was greater. The average grain amylopectin content of superior grains of N0, N90, N180 treatment and inferior grains of N0 treatment on the secondary branches was more than primary branches, excluding the inferior grains of N90 and N180 treatment. At the same time, average amylopectin content reduced with increasing nitrogen application, the same superior grains as inferior grains. Enrich the better part of (superior grains) or to deal with (N0) amylopectin content between the differences are mainly on the grains caused by primary branches. And enrich the poor, parts or treatments, and there amylopectin content in addition to the differences in grain arising from the secondary branches, grains at primary branches was also a source of differences between treatments.The whole grain-filling stage, amylopectin content also showed the trend of the accumulation of "S"-type changes, Inferior grains, the differences of starch content between N90 and N180 treatments and N0 treatment started in the early filling stage, the difference of amylopectin content between N90 and N180 treatments was at 15 days after flowering to spend a larger share, differences of starch content between treatments caused by the different amylopectin content. Grain amylose content changes in mixed at one day, while grain amylopectin content had shown a rising trend. Daily changes of amylopectin content or amylose content at early and middle grain filling stage were larger, later stage, daily changes were less. Daily changes of amylopectin content or amylose content of inferior grains at 20-30 days after anthesis were directly on a larger range. Most of the period, daily changes of three treatments were the same trend line, especially the N90 and N180, but at different grain filling, the differences at three treatments increasing in starch content appeared in any time of one day.At the whole grain filling period, the total grain starch content was basically the same trend as the increasing trend of grain dry weight, was "S"-type changes. In maturity, the total starch content of superior and inferior grains of N0 treatment were larger than those of N90 and N180 treatment. Diurnal variation of starch accumulation and grain dry weight accumulation were slightly different from the diurnal changes, the changes in grain dry weight was the law, and the diurnal variation of starch accumulation was relatively more complicated. In general, the average of starch accumulation rate was still faster than at night. Relatively , starch content of superior grains accumulated fastly in 10-20 days after anthesis, the differences of starch content between treatment were more complex. Inferior grains, the rate of starch accumulation of N0 treatment was significantly faster than the N90 and the N180 treatment at 10-30 days after anthesis, three deal with the differences between the starch accumulation was more complex, compared to the other two treatment, the rapid starch accumulation period of N0 treatment was not fixed, but at different stages starch accumulation was not the same as on the changes. Correlation Different time of day rate of change in starch accumulation with 1000-grains weight of superior and inferior grains was mostly not significant in the micro-environment, changes in starch accumulation in the three treatments showed as more complex laws.8 At early grain filling period, the ADP-glucose pyrophorylase (AGPP) activities was lower, and then the activities of N0 treatment began to rise, while the activities of N90 and N180 treatment had a slight decrease in the mid-filling, followed by a rapid increase in activity began. To 35 days after flowering, the peak of activities was at this time, and the activity of N90 treatment was slightly higher than those of N0 and N180 treatment. The differences of N0,N90,N180 treatment in activities, mainly in 22 - 29 days after flowering. At 22 days after anthesis and 29 days after anthesis the AGPP activities levels of three treatment followed by N0> N90> N180, while the enzyme activities differences of N90 and N180 treatment in 22-35 days.Soluble starch synthase (SSS) activities of inferior grains were "S"-type changes at grain filling stage, that is, before the early grain filling stage the activities was lower, at the middle grain filling stage the activities increased rapidly, and at the late grain filling of 29 days after anthesis the activites reached the peak, followed by a slight decline in activity to 35 days after anthesis, N0 and N90 treatment had similar activities, were significantly higher than that of N180 treatment. Grouting period from the beginning, the differences of the activities of three treatments was significantly or extremely significantly, that is, the activity between treatments were increased by applied more nitrogen fertilizer.Granule-bound starch synthase (GBSS) activity of the entire filling period was also "S"-type changes, in the early grain filling stage (15 days after anthesis) the activities decreased slightly, at middle grain filling stage started to rapidly increase in activities, and at 29 days after flowering reached the peak, followed by enzyme activities rapidly declined. In the early grain filling (10-15 days after flowering) the activities had no obvious difference between treatment, activities in the mid-and late grain filling stage (22-35 days after anthesis) the larger the differences, the levels of the activities between treatments followed by N0> N90> N180.At the whole grain filling stage , the relation of three enzymes activities with grain plumpness were close, AGPP activities at 10,22,29 days after anthesis had a significantly or extremely significantly positive correlation. SSS had the most closely related to grain plumpness of inferior grains, at the whole grain filling stage SSS activities had significantly or extremely significantly positive correlation with grain plumpness of inferior grains. GBSS activities in 22-35 days after anthesis had significantly positive correlation with grain plumpness. Correlation of SSS activities in the whole grain filling period with grain plumpness of inferior grains was close, and only AGPP and GBSS activities in some time had an close relation with inferior grains plumpness.At the whole grain filling stage, daily changes in AGPP activity was law, in the early grain filling stage was "V"-type changes, in the mid-and late grain filling stage was "W"-type changes .In the grain filling period, with the exception of the peak activity period at 29 days after anthesis, the time point of the highest activities at the others grain filling stages were at 19:00, and the activities of the others points was lower. And daytime and nighttime activity does not have large differences, and consistent performance between treatments. The activities of N0 treatment was higher than the others treatments mainly at night, grain filling in different time periods in which slightly different.Daily changes of SSS activities during different grain filling stage had different trends, the three treatments at early and late grain filling stage had the same trend, only the mid-filling, three treatments had different trends. SSS enzyme in addition to peak 29 days after anthesis had been increased activity in the whole day, the remaining grain filling stage of activities during the day was basically over night, especially N0 treatment. The time point at which the activities of N0 treatment was higher than N90 and N180 treatment, at different grain filling stage between treatments was different.Daily changes of GBSS activities during different grain filling stage had different trends, the N90 and N180 treatment had similar trends at the whole grain filling stages, and the changes of N0 treatment had different trend with N90, and N180 treatments. During the day and at night the size of activities, with the exception of the activities of N0 treatment at 10-15 days after anthesis and at 29 days after anthesis at night were higher than the day, in the remaining period or treatments the activities of the enzymes were greater at the day. Grain filling stages at which the activity of N0 treatment was higher than that of N90 and N180 treatment was not fixed.At different grain filling stage, the correlation of the enzymes activities of diurnal variation with grain plumpness did not showed as the same. In the entire grain filling stage ,the time point at which the correlation of AGPP activities of three treatments with grain plumpness was larger was at the night (19:00-7:00) ,and during the day were basically not significant or a significant negative correlation. The SSS activity at the day and night had a very close correlation with grain plumpness, and night-time activity at late grain-filling stage had a positive correlation. The relationship of GBSS activity during the day with grain plumpness does not close, and at night the activity was closely related with the grain plumpness, in particular, the activity of 1:00 at night. It showed that grain plumpness and grain sink activity had a closely relation, at the whole grain filling stage, grain plumpness and SSS were most closely related to activity, SSS activity during the day and night had a very close relationship with grain plumpness, and AGPP and GBSS only at night had a close relations, and SSS and GBSS associated with the night more than AGPP.9 At grain filling stage, hormone changes in single of endogenous hormone zeatin (ZR), gibberellin (GA), auxin (IAA) and abscisic acid(ABA) content increased with the conduct of grouting , at 10-15 days after anthesis, the hormone content remained unchanged, only IAA content within 15 days after anthesis than 10 days after anthesis decreased slightly. After 15 days after flowering the beginning of a rapid increase in hormone content, ZR and ABA in 29 days after flowering reached the peak, followed by a slight decline, while the GA and IAA had been increased to 35 days after flowering peak, GA levels in 29-35 days after anthesis has been a rapid increase, while the IAA content of 29-35 days after anthesis increased only trace. N0 treatment in the entire grain filling stage had a significant or extremely significant difference, and N90 treatment after 15 days after flowering hormones was significantly or extremely significantly higher than the N180 treatment, at 10-15 days after anthesis the difference of hormones of N90 treatment and N180 treatment. Show that, the differences of N90 and N180 treatment between the hormone content was mainly at the middle and late grain filling stage. Combined with the hormone content of grain and grain plumpness, the maximum starch accumulation rate, the average rate of starch accumulation, we can see the correlation of the endogenous hormone with grain plumpness and starch accumulation rate were a positive, with the exception of 10,15 days after anthesis the content of GA and the enrichment and grain starch accumulation rate was not significantly related, at the remaining period the hormones content with grain plumpness and starch accumulation rate reached a significantly or extremely significantly positive correlation. It shows that during grain-filling four hormones of inferior grains had a very close relation with grain plumpness and starch accumulation rate, so higher ZR, IAA, ABA content of inferior grains at grain filling stage and in the middle and late grain filling stage the higher GA content were helpful to higher grain plumpness.Daily changes of different kinds of hormones and different periods had different trends. The differences of hormones content between treatments at most of the time points were expressed as the increase in nitrogen applied with the reduction. And the day and the night had not significant difference in hormones content.At different grain filling stage, four hormones content at all time points of one day were basically significantly or extremely significantly positively correlated with grain filling rate and grain plumpness. It shows that high hormones content of inferior grains had favor to grain filling in the whole grain filling stage. The entire grain-filling stage ABA and ZR content had the most closely correlation with grain plumpness and grain filling rate. GA was only at 15,22 days after anthesis had a close correlation with grain plumpness and grain filling rate, at others grain filling stage was only had a point in time at which GA content had a significant or extremely significant correlation with grain plumpness and grain filling rate. IAA was only at 22,29 days after anthesis had a close correlation with grain plumpness and grain filling rate, at others grain filling stage was only had a point in time at which IAA content had a significant or extremely significant correlation with grain plumpness and grain filling rate.
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