| The yield of rice consists of accumulation of starch in caryopsis.Fertilizer nitrogen and potassium are more important on synthesis and accumulation of starch of rice caryopsis.However,there has been not elucidated the physiological mechanism of effect of nitrogen and potassium on starch synthesis.Aim to that,this experiment,Nanjing 9108（japonica rice）used as the material with caryied（trial 1）pure nitrogen 0 kg·hm-2,90kg·hm-2,135 kg·hm-2,180 kg·hm-2,4 nitrogen application levels,respectively by N0,N1,N2,N3,with N0 as the control,set（trial 2）pure potassium 0 kg·hm-2,90 kg·hm-2,135kg·hm-2,180 kg·hm-2,4 potassium application levels,as K0,K1,K2,and K3,K0 was used as a control,respectively,effects of different nitrogen and potassium levels on the enzyme activity and starch accumulation of starch synthesis were investigated.The objective was to clarify the influence of varied nitrogen and potassium application amount on starch accumulation,related enzyme activities and starch synthesis,and to offer theoretical element for the rational application of nitrogen and potassium fertilizers.The results showed,as followed:1.Effect of nitrogen application on caryopsis starch synthesis（1）Result of two-years trial was that the sucrose content in caryopsis was a trend of rising first and then down with growth procesing.The sucrose content peaked 15 days post anthesis and raised with the increase of nitrogen application,N3 was 33.42%,31.59%and22.49%higher than N0,N1 and N2,respectively,averagely.During maturity period（30days post anthesis）,Nitrogen application was beneficial to raise the content of sucrose in caryopsis but trend of surcose content in two-year experiment was inconsistent.The of glucose and fructose content decreased with the growth procesing,reaching a peak at 10days after anthesis,it suggested a trend of increasing first and then down with the increasing of nitrogen application.The content of fructose under N2 treatment was 49.25%,33.27%,and 11.79%higher than N0,N1,N3 averagely,respectively.The glucose content under N2 treatment was 50.42%,41.87%,and 9.40%higher than N0,N1,and N3,averagely,respectively.During the mature period（30 days post anthesis）,the glucose content raised with the rising of nitrogen application.Nitrogen application was beneficial to raise the content of fructose in caryopsis but trend of fructose content in two-year experiment was inconsistent.（2）The activity of AGPase,BE,and DBE enzymes raised first and then down with the increasing of nitrogen application under range of nitrogen application 0-180 kghm-2.The enzymes of AGPase and SSs reached a peak at 10 days post anthesis,and the activity of AGPase raised first and then down with the increasing of nitrogen application,N2 was8.46%,0.47%,and 7.94%higher than N0,N1,and N3,respectively,activity of SSs raised with the rising of nitrogen application,N3 was 65.04%,35.00%and 30.01%higher than N0,N1 and N2,respectively.The activities of GBSS,BE,and DBE reached a peakat 15days post anthesis,and the GBSS activity raised with the increasing of nitrogen application,N3 was 20.45%,5.42%,and 5.29%higher than N0,N1,and N2,respectively.Activity of BE and DBE raised first and then down with the rising of nitrogen application.N2 treatment of BE was 25.07%,13.80%and 16.00%higher than N0,N1 and N3,respectively,N2 treatment of DBE was 25.72%,10.16%and 6.35%higher than N0,N1 and N3,respectively.（3）The yield of rice increased with the rising of nitrogen fertilizer,N3 treatment was bette.Under N1 and N2 treatment conditions,the peak viscosity and the breakdown value was high,the setback value was lower than other treatments,and the cooking quality was better.The accumulation of amylopectin and total starch were rising first and then down with the increasing of nitrogen application under range of nitrogen application 0-180kghm-2.During the maturity period（30 days post anthesis）,N2 treatment of amylopectin was 18.01%,9.20%,and 6.19%higher than N0,N1,and N3,respectively.N2 treatment of total starch was 16.31%,8.70%,7.82%higher than N0,N1,and N3,respectively,averagely.The ratio of amylose to amylopectin reduced under N2 treatment.The regulation of nitrogen fertilizer on amylose accumulation varied from year to year,during the maturity period（30 days post anthesis）,the accumulation of amylose raised with the increasing of nitrogen application,N3 was 10.67%,10.64%,and 7.49%higher than N0,N1N2,respectively in 2018,the accumulation of amylose was a trend of rising first and then down with the increasing of nitrogen application.N2 was 12.93%,10.79%,and 2.95%higher than N0,N1,and N3,respectively,at the mature stage（30 days post anthesis）in 2019.2.The effect of potassium application on caryopsis starch synthesis（1）The two-year trial was that the sucrose content in caryopsis was a trend of increasing first and then down as the growth procesing,reaching a peak 15 days post anthesis and showing a trend of rising first and then down with increasing of potassium application,K2 treatment was 119.89%,55.08%,and 22.52%higher than K0,K1,and K3,averagely,respectively.At maturity（30 days post anthesis）,the sucrose content in caryopsis raised with increasing of potassium application.The glucose and fructose contents decreased as the growth procesing,reaching a peak at 10 days post anthesis,the glucose content was a trend rising first and then down with the increasing of potassium application,K2 treatment was 183.73%,86.46%,and 91.57%higher than K0,K1,K3,averagely,respectively.The glucose content in caryopsis raised with increasing of potassium application during the maturity period（30 days post anthesis）.Potassium application was beneficial to raise the content of fructose in caryopsis but trend of fructose content in two-year experiment was inconsistent.（2）The enzymes activity of AGPase,SSs,GBSS,BE,and DBE in caryopsis were rising first and then down with the rising of potassium application under range of potassium application 0-180 kghm-2.The enzymes of AGPase and SSs were peaking at 10days post anthesis,activities of AGPase and SSs were increasing first and then down with the rising of potassium application,K2 treatment of AGPase was 1.1%,73.74%,42.96%higher than K0,K1,K3 respectively,K2 treatment of SSs was 98.31%,43.26%,2.63%higher than K0,K1,K3,respectively.The activities of GBSS,BE,and DBE were peaking at 15 days post anthesis,showing a trend of rising first then down with the increasing of potassium application,K2 treatment of GBSS was 35.08%,14.95,21.22%higher than K0,K1,K3 respectively,K2 treatment of BE was 59.67%,34.74%,and 19.57 higher than K0,K1,and K3,respectively.K2 treatment of DBE was 22.56%,9.86%,and 15.97%higher than K0,K1,and K3,respectively.（3）The rice yield was a trend of rising first and down with the increase of potassium fertilizer.The K2 treatment was the optimum treatment with value of peak viscosity,breakdown higher than other treatments,and setback value lower than other treatments,and the cooking quality was better.The accumulation of amylose,amylopectin and total starch in caryopsis were a trend of increasing first and then down with the rising of potassium fertilizer(0-180 kghm-2).During the maturity period（30 days post anthesis）,K2treatment of amylose was 21.40%,11.84%,and 4.63%higher than K0,K1,and K3,respectively,and K2 treatment of amylopectin was 20.36%,11.63%,8.34%,higher than K0,K1,and K3,respectively,K2 of total starch was 20.61%,11.68%,and 7.42%higher than K0,K1,and K3,respectively.The ratio of amylose to amylopectin reduced under K2treatment.In conclusion,considering the yield and quality of rice comprehensively,the experiment supported that the content of sucrose,glucose and fructose in caryopsis increased,the activity of enzymes related to starch synthesis regulated and promoted the formation of starch components,reduced the ratio of amylose to amylopectin in caryopsis,improved rice yield and rice quality when the amount of nitrogen was 135kghm-2and the amount of potassium was 135 kghm-2. |
