Effects Of Different Nitrogen Forms On The Mehcanism Of Nitrogen Use Efficiency In Wheat (Triticum Aestivum L.) Cultivars With Specialized End-Uses

In this study, three different types of winter wheat （Triticum aestivum L.） cultivars with specialized end-uses Yumai 34 with strong gluten, Yumai 49 with medium gluten and Yumai 50 with weak gluten were planted in pot of field, respectively, to be used for investigation of utilizing efficiency of NO₃^--N, NH4+-N, NH₂--N as well as their spatio-temporal dynamic and molecular and physiological mechanism in order to illustrate the utilizing efficiency of different kinds of nitrogen and regulating mechanism of nitrogen metabolism of winter wheat cultivars with specialized end-uses, which can provide the theoretical and practical basis of improving using efficiency of nitrogen and techniques of how to develop the special wheat with high quality and yield.The following is the main results in this study.1.The potted special wheat plants in field were examined and evaluated for producing efficiency, using efficiency, absorption efficiency, harvest index, transporting efficiency and contributing efficiency of nitrogen under the different treatments.Results indicated that there are the obvious differences on yield, quality, nitrogen use efficiency of in three special wheat cultivars, which are significantly influenced by the form of nitrogen.Furthermore, analysis of yield, producing efficiency and utilizing efficiency of nitrogen indicated that weak-gluten wheat cultivar Yumai 50 is higher than medium-gluten cultivar Yumai 49 and the later is higher than strong-gluten cultivar Yumai 34.The kernel protein content and utilizing efficiency, harvest index, transporting efficiency, contributing efficiency of nitrogen of Yumai 34 are highest and those of Yumai 50 are lowest among them.Comparison of the same cultivar with different treatment of conformation nitrogen, strong-gluten cultivar Yumai 34 possessed highest producing efficiency, utilizing efficiency and harvest index of nitrogen under the treatment of NO₃^--N, whereas transporting efficiency and its contributing efficiency of nitrogen is highest under the treatment of NH₂-N.The producing efficiency, absorption efficiency of nitrogen and yield of medium-gluten cultivar Yumai 49 are highest in the treatment of NH₂-N, and its utilizing efficiency, harvest index, transporting efficiency and contributing efficiency of nitrogen as well as protein content are improved under the treatment of NH₄⁺-N.For weak-gluten cultivar Yumai 50, producing efficiency and absorption efficiency of nitrogen are highest in NH₄⁺-N, while utilizing efficiency, harvest index and transporting efficiency of nitrogen are higher in NO₃^--N, and contributing efficiency of transportation nitrogen is highest in NH₂-N.Therefore, different conformation of nitrogen should be selected for breeding different special wheat cultivars with high quality and yield.2.The potted wheat plants in field were used to identify the effect on root characters and morphological rhizosphere of soil nitrogen, related-transportation microorganism, enzyme activity of different conformational nitrogen . Results indicated that the numbers and activity of root in strong-gluten cultivar Yumai 34 are highest in NO₃^--N, and the numbers, biomass and activity of root in medium-gluten cultivar Yumai 49 are highest in NH₂-N, and the biomass and activity of root in week-gluten cultivar are highest in NH₄⁺-N but its number of root is less than that in NH₂-N.Among the number, biomass and activity of root, the activity of root have an intimate relationship with absorption efficiency of nitrogen and wheat yield.During the whole growing stage, the change of soil microbe of rhizoshpere and protease activity showed the inverse“V”shape.In strong-gluten cultivar Yumai 34, urease, protease and activity of ammonifying bacteria could be obviously improved when the treatment of NO₃^--N while the treatments of NH₂-N and NH₄⁺-N could increase the activities of nitrobacteria and nitrosobacteria.In medium-gluten cultivar Yumai 49 and weak-gluten cultivar Yumai 50, the treatment of NH₂-N could improve the activities of ammonifying bacteria, urease and protease while the treatment of NH₄⁺-N could increase the activities of nitrobacteria and nitrosobacteria.Of them, it showed urease > nitrobacteria > nitrosobacteria > protease > denitrifying bacteria > ammonifying bacteria, and the activity of nitrosobacteria is five times of ammonifying bacteria.3.The potted plants in field were used to identify changing characters of nitrogen content in whole plant and special organism treated by different conformation of nitrogen on 8 characteristics of flag leaf, the second, third and forth leafs counted from the top, stem, sheath, glume, rachilla and kernel, respectively, and to evaluate the transporting efficiency and its contributing efficiency.Results indicated:1) the nitrogen content of leaf is significantly higher than those of other organisms during the whole stage and nitrogen content gradually reduced with the decrease of leaf position.The highest nitrogen content of plant and different organisms are all present in flowering time and the difference of nitrogen content of plant and different organisms showed the most obvious at shooting and flowering the stages as well as seven days after anthesis.2) The strong-gluten cultivar Yumai 34 possessed higher nitrogen content in whole plant and different organisms than those of Yumai 49 and Yumai 50.The conformation of nitrogen significantly influenced on nitrogen content in whole plant and different organisms.Yumai 34 and Yumai 50 possessed highest nitrogen content under the treatment of NH₂-N but the highest nitrogen content of Yumai 49 presented in treatment of NH₄⁺-N.Of them, leaf have been the most biggest impacted amongst them, especially for the second leaf counted from top.3) the contributing rate from absorption nitrogen to transportation nitrogen is between 66.01%-81.29% before anthesis.The contribution rate of leaf is significantly higher than those of other organisms and it gradually reduced with the decrease of leaf position.Among three special wheat cultivars, strong-gluten cultivar Yumai 34 showed the highest contribution rate with 71.05%-81.29%, and medium-gluten cultivar Yumai 49 and weak-gluten cultivar 50 are 68.63%-72.77% and 66.01%-71.02%, respectively.Therefore, the effect of conformation of nitrogen on contribution rate of special wheat cultivars is consistent with nitrogen content, i.e.the strong-gluten and weak-gluten cultivars are highest in NH₂-N but the medium-gluten cultivars is highest in NH₄⁺-N.4.The potted wheat plants were used to investigate the influence of different forms of nitrogen on nitrate nitrogen, free amino acid and soluble protein of special wheat plants.Results indicated that:1) nitrate nitrogen content of stem with 4 times range of leaf and 10 times range of root is highest and changes a lot in different periods, and the second is sheath, the third is leaf.The summit period of nitrate nitrogen content in stem is flowering stage and others are in jointing stage.The nitrate nitrogen content in kernel is the highest on the 7th day after anthesis and is only lower than those of stem and sheath.2) The free amino acid content of leaf is relatively higher and mainly concentrates in flag leaf and the second leaf counted from top while the third and forth leafs counted from top possessed relatively lower free amino acid content.The free amino acid contents of stem and sheath are relatively lower.The free amino acid content on the 7th day after anthesis is highest in different growing stage and after that it gradually decreased.The assimilation of nitrogen is mainly in leaf, especially in flag leaf and the second leaf counted from top as well as glume and spike axis, which played the more important role on assimilation of nitrogen than the third and forth leafs counted from top.3) The soluble protein in different organisms gradually decreased with the growing of wheat plant and the summit time ranged in different organisms.Of them, the soluble protein in flag leaf and second leaf from top of strong-gluten cultivar Yumai 34 possessed summit time on the 7th day after anthesis, and for medium-gluten cultivar Yumai 49 and weak-gluten cultivar they are flowing stage.In wheat kernel, the soluble protein is the highest on 7th day after anthesis and is the lowest on 14th day and then gradually increases until the 21st day.4) It showed the significant influence of different conformation of nitrogen on the content and changing degree of above-mentioned three characters.In strong-gluten cultivar Yumai 34, the content and changing range of three characters are biggest under the treatment of NH₂-N while medium-gluten cultivar Yumai 49 is in NH₄⁺-N and weak-gluten cultivar Yumai 50 is in NH₄⁺-N for soluble protein and NH₂-N for the range of nitrate nitrogen and free amino acid.5.The potted wheat plants in field were used to examine the effect of conformation of nitrogen on key enzyme for wheat metabolism GS isozyme. Results indicated that:1) GS isozyme are prevalent in seedling leaf, differently positional leaf after anthesis, differently positional stem and kernel.Three GS isozyme of GS1, GS2 and GS3 were identified in seedling leaf, four GS isozyme of GS1, GS2, GSX and GSX2 were found in differently positional leaf after anthesis but only one isozyme GS1 was found in kernel.The activity of GS1 is stable in different organism and it expresses in all growing stage, whereas GS2, GSX and GSX2 are only in the leaf and stem with vigorous function of metabolism.2) Nitrogen forms significantly regulated GS activity in seedling stage and the GS activity in the strong-gluten cultivar Yumai 34 was increased under the treatment of NH₂-N but it decreased after plant reached three leafs under the treatments of NO₃^--N and NH₄⁺-N.The GS activity in medium-gluten cultivar Yumai 49 was increased under the treatment of NH₄⁺-N but it decreased after plant reached two leafs under the treatments of NO₃^-N and NH₂-N.The GS activity in weak-gluten cultivar Yumai 50 had not decreased under the three treatments of nitrogen and GS activity was the highest under the treatment of NH₄⁺-N.3) In the later growing stage of wheat plant, GS activity was highest in leafs of Yumai 34 under the treatment of NH₂-N, Yumai 49 under the treatment of NH₄⁺-N and Yumai 50 under the treatment of NH₂-N, which was quite similar to effect of morphological nitrogen on stem.In kernel, GS activity was the highest under the treatment of NH₂-N.The treatment of NH₄⁺-N could induce the express of GSX2 in different positional leafs.The treatment of NH₂-N increased the GS2 and GSX activity in all growing stage of Yumai 34 while the treatment of NO₃^--N could inhibit the GS2 activity.NH₄⁺-N could contribute to the express of GSX an GS2 genes on the flowering stage, 7th and 21st days after anthesis of Yumai 49.The treatment of NH₂-N increased the GSX and GSX2 activity on the flowering stage, 7th and 21st days after anthesis of Yumai 50.