Research On The Root Characteristics Of Nitrogen Uptake And Metabolism Of Wheat Cultivars With Different Nitrogen Efficiency

Wheat is one of the most important cereal crops in China.A series of environmental problems have appeared,such as nitrogen losses and non-point source pollution,because of the nitrogen fertilizer was used unreasonably and excessively.Improving the nitrogen efficiency of wheat,by selecting and breeding varieties of high nitrogen efficiency,is the key to solve the contradiction between high yield and environment protection.The nitrogen uptake capacity of root is the basis of nitrogen metabolism in wheat,which directly related to the nitrogen assimilation,nitrogen transfer and the synthesis of amino acids and proteins of the aboveground parts,and influences the nitrogen uptake and utilization of wheat.So the yield,N-efficiency,relationship between root and shoot,root nitrogen uptake and nitrogen metabolic characteristic of eight wheat cultivars were researched under three nitrogen application levels(120(N8)、225(N15)、330(N22)kg N·hm-2)with field-pot experiment.In our study,wheat cultivars belong to different N-efficiency types,they were high nitrogen high efficiency(HH)type: Zhengmai 366 and Zhoumai 27,high nitrogen low efficiency(HL)type:Zhoumai 28 and Kaimai 20,low nitrogen high efficiency(LH)type: Luomai 18 and Yumai49-198,low nitrogen low efficient(LL)type: Xinong 509 and Aikang 58.The main results were as follows:Under the three nitrogen application levels,the yield of different N-efficiency types wheat cultivars showed that Zhengmai 366 and Zhoumai 27 higher than Zhoumai 28 and Kaimai 20,and Luomai 18 and Yumai 49-198 higher than Xinong 509 and Aikang 58.Wheat yield of all varieties increased with the increasing of nitrogen application.Compared with N15,the normal nitrogen application levels,the yield decreasing amplitude showed HH lower than HL,LH lower than LL in N8,significantly.In N22,the yield increasing amplitude showed HH lower than HL,Yumai 49-198 of LH lower than Luomai 18 of LH and LL.The NUTE(nitrogen utilization efficiency),NPE(nitrogen physiological efficiency),NUPE(nitrogen uptake efficiency)of all varieties decreased with the increasing of nitrogen application.Under the three nitrogen application levels,the NUTE,NPE,NUPE all showed HH higher than HL,LH higher than LL.Indicated that the high N-efficiency genotyps had higher nitrogen uptake efficiency as well as nitrogen utilization efficiency.Nitrogen accumulation and distribution ratio of different N-efficiency types wheat cultivars showed grain> vegetative organs> root,and the nitrogen accumulation of the plant and different organs increased along with the nitrogen application.Under the three nitrogen application levels,the plant nitrogen accumulation showed Zhengmai 366 and Zhoumai 28 higher than Zhoumai 27 and Kaimai 20,Luomai 18 and Yumai 49-198 higher than Xinong509 and Aikang 58.The grain nitrogen accumulation showed the HH higher than HL,and LH higher than LL,significantly.Indicated that the high N-efficiency genotyps had higher nitrogen absorptive capacity and the ability of nitrogen distribution to grain.Under the three nitrogen application levels,HH compared to HL.Root dry weight showed that Zhoumai 28 was maxium,Zhengmai 366 and Zhoumai 27 took second place,and Kaimai 20 was minium.When LH compared LL,Root dry weight showed that Aikang 58 was maxium,Luomai 18 and Yumai 49-198 took second place,and Xinong 509 was minium.Comparison between different nitrogen treatments,the root dry weight of Zhoumai 27,Zhegnmai 366,Kaimai 20,Yuamai 49-198 reached the maximum at N15.And the root dry weight of Zhouamai 28,Luomai 18,Xinong 509 and Aikang 58 increased as the increasing of nitrogen application,reached the maximum at N22.Indicated that the high N-efficiency genotyps had higher root biomass as well as reasonable relationship between root and shoot.The root vigor,total root absorb areas and root active absorbing area of all varieties increased with the increasing of nitrogen application,that is N8>N15>N22.Under the three nitrogen application levels,the root vigor showed the HH higher than HL significantly,and the total root absorb areas and root active absorbing area showed that Zhoumai 28 was maxium,Zhengmai 366 and Zhoumai 27 took second place,and Kaimai 20 was minium,when HH compared to HL,significantly.Compared LH to LL,the root vigor,total root absorb areas and root active absorbing area all showed the LH higher than LL,significantly.Indicated that the high N-efficiency genotyps had higher total root absorb areas and root active absorbing area as well as root vigor.The GS activity,NR activity,free amino acids concentration,soluble protein concentration,nitrate concentration and ammonium concentration in root of all wheat cultivars increased along with the improving of nitrogen application.Under the three nitrogen application levels,the GS activity,NR activity,free amino acids concentration and soluble protein concentration in root showed HH higher than HL,and LH higher than LL,significantly.While the nitrate concentration and ammonium concentration in root showed HH lower than HL,and LH lower than LL,significantly.Indicated that the high N-efficiencygenotyps had higher key enzymes activity of nitrogen assimilation and metabolic capability in root.