| The seeds of Tartary buckwheat are rich in active ingredients such as flavonoid,and they are medicinal and edible cereal crops.Its endosperm is the main utilization part of grain,and its development directly determines the yield and quality of crops.Nitrogen is an essential element for crop growth and development,and one of the main environmental factors that can be regulated in agricultural production.Many studies have been done on the effect of nitrogen application on grain yield,quality,grain filling process and grain development of wheat and rice,but few on starch formation of Tartary Buckwheat.In order to clarify the effects of different levels of nitrogen on dry matter accumulation,grain filling,starch formation and accumulation,and the filling process of starch grains in endosperm,a field experiment was carrie out in the arid and semi-arid areas of the Loess Plateau under different nitrogen treatments,0 kg/ha,90 kg/ha,180 kg/ha,270 kg/ha.The Tartary buckwheat cultivar,Xinong 9940 and Qianku 3 were selected for the study.Main conclusions are as follows:1.Tartary buckwheat growth and development,dry matter accumulation and transport and its contribution to grain changes under different nitrogen levelsThe plant height,chlorophyll content and dry matter accumulation of stem and leaf of tartary buckwheat increased with the increase of nitrogen application.There are differences in performance due to the variety.Xinong 9940 showed N2> N3> N1> N0,and there was no significant difference between N2 and N3 treatments.Qianku 3 showed N3> N2> N1> N0,with significant differences among the treatments.Overall,the dry matter accumulation of stem and leaf of Qianku 3 was higher than that of Xinong 9940.Qianku 3 showed higher dry matter accumulation of stem and leaf and was more sensitive to nitrogen response.Nitrogen fertilizer can promote the transfer of dry matter to grains in the early stage of grain filling and increase the yield of Tartary buckwheat.At the same nitrogen application level,the transfer rate and contribution rate of Tartary buckwheat leaves to grains were higher than that of stems.At the same nitrogen application level,compared with Qiangu3,Xinong 9940 nutritive organ dry matter contributed less to grains.2.Changes in grain weight and grain filling parameters under different nitrogen levelsThe 1000-grain weight of Tartary buckwheat increased gradually with the filling process,and the nitrogen application significantly increased the grain weight.Logistic equation was used to fit the grain filling process under different nitrogen application conditions,and the r reached 0.996?0.999,and the filling process of different Tartary buckwheat varieties with different nitrogen application levels was consistent with the "S" growth curve.According to the filling parameters,nitrogen application significantly affected the maximum filling time,duration and average rate of Tartary buckwheat grain,shortened the increasing period,prolonged the fast increasing period and the slow increasing period,and improved the dry matter accumulation in each stage.Compared with Qianku 3,Xinong 9940 had a faster grouting rate,a longer grouting duration and a larger grain weight.The grout duration,average grout rate,fast grout period,slow grout period,and dry matter accumulation in three stages were positively correlated with 1000-grain weight(P<0.01).There was no significant correlation between the maximum grout rate,the increasing period time,the increasing period grout rate and the 1000-grain weight.3.Changes in starch synthesis and accumulation under different nitrogen levelsThe content of Tartary buckwheat starch and its components and enzyme activity related to starch synthesis were significantly increased by nitrogenous fertilizer application,while excessive nitrogenous fertilizer application had an inhibitory effect.At the same nitrogen application level,the contents of Qianku 3 starch and its components were higher than those of Xinong 9940,and the changes of Qianku 3 amylose content were more sensitive to nitrogen application,while the changes of Xinong 9940 amylose content were more sensitive to nitrogen application.The enzyme activities of ADPG-PPase,GBSS,SSS and SBE of Tartary buckwheat starch synthesis all showed a single peak curve,and all reached the peak at 15 d after flowering.With the increase of nitrogen application,the activity of starch synthetase related to starch synthesis increased first and then decreased.4.The effect of nitrogen on the accumulation of starch granules in endosperm tissueThe application of nitrogen could increase the length and width of the endosperm cells of Tartary buckwheat,enlarge the "reservoir" for storing dry matter,and increase the grain weight.The starch granules in Tartary buckwheat endosperm cells were mostly elliptic and single grains.Nitrogen application promoted the accumulation of starch granules in early stage.With the progress of grouting,the filling of starch granules and nitrogen application delayed the decay of nucleus,promoted the division of endosperm cells,increased the number of endosperm cells,and thus regulated the change of contents of starch and its components in grains,thus increasing grain weight and promoting the increase of yield.5.Changes in yield and yield components under different nitrogen levelsWith the increase of nitrogen application level,the number of flower clusters per plant,grain number per plant,grain weight per plant and yield of Xinong 9940 increased first and then decreased,which were all optimal at 180 kg/ha.The yield,grain number per plant and grain weight per plant of Qianku 3 gradually increased and reached the maximum value at 270 kg/ha.The yield increase of Qianku 3 was higher than that of Xinong 9940 after adding nitrogen fertilizer,and it was sensitive to nitrogen fertilizer.The correlation analysis showed that the grain number,grain weight and grain yield per plant were significant or extremely significant,indicating that the grain weight per plant played a very important role in the improvement of Tartary buckwheat yield.In summary,nitrogen application significantly affected the overground growth of Tartary buckwheat,and significantly promoted the biomass accumulation of plant height,chlorophyll content,stem and leaf.Nitrogen application significantly increased the buckwheat endosperm cell volume growth,promote the early accumulation of starch grains,delayed the decline and fall of the nucleus,promote cell division,expand the "library" capacity,to extend the duration grouting,grouting,at an average rate shorten the growing period,prolong the quick increase period time gentle increase period,improve the various stages of the dry matter accumulation,improve the starch synthase,and promote the synthesis of starch and the accumulation,eventually improve the buckwheat production,but excessive nitrogen decreased the ability of starch synthesis,the increase of grain weight.The results of this study showed that in the arid and semi-arid regions of the loess plateau,the optimal nitrogen application amount of Tartary buckwheat was 180?270 kg/ha,and the response sensitivity of different varieties to nitrogen fertilizer was different,so the appropriate nitrogen application amount should be selected according to the habitat environment and varieties. |
PDF Full Text Request