Preliminary Study On Nitrogen Response Of Rice At Tillering Stage

The tillering stage is a key period for rice to be sensitive to nitrogen supply.In order to explore the difference of the effect of rice varieties on the treatment of different concentrations of nitrogen in the tillering stage,three rice varieties Huanghuazhan,IR38 and Guichao2 with wide planting area and close development stage and different variety characteristics were selected in this study.The above three varieties were treated with nitrogen gradient in the tillering stage by hydroponics.The phenotypes of three rice varieties under different treatments were investigated,including leaf age,SPAD value,number of tillers and biomass.The enzyme activities and gene expression related to carbon and nitrogen metabolism were further analyzed.The main results were as follows:1.Combined with phenotypic data such as leaf age,SPAD value,tiller number and dry matter weight,the results showed that,among the three rice varieties,Huanghuazhan is the most sensitive to low nitrogen treatment and be impacted greatest,indicating that Huanghuazhan is a variety intolerant to low nitrogen,Guichao 2 is insensitive to low nitrogen treatment,indicating that Guichao 2 is a low nitrogen tolerant variety.IR38 had a better adaptability to low nitrogen than Huanghuazhan,and it could recover from the lack of nitrogen environment quickly.In addition,the effect of high nitrogen on Huang Huazhan and Guichao2 is smaller than IR38.These results indicates that rice varieties have different reactions to high nitrogen and low nitrogen,and the varieties sensitive to low nitrogen may not be sensitive to high nitrogen treatment,and vice versa.2.Low nitrogen treatment significantly inhibited the expression of AMT1;1,Os NAR2.1 in the roots of Huanghuazhan,which led to the lack of nitrogen in the plant and then affected the activity of nitrogen assimilation related enzymes such as NADHGOGAT2 and NR,which led to the inhibition of the overall carbon and nitrogen metabolism of the plant.However,low nitrogen treatment can promote nitrogen nitrogen absorption and translocation in Guichao2.The relative gene quantitative data showed that low nitrogen could significantly promote the expression of AMT1;1,AMT1;2,Os NRT1.1B and so on,so it would not affect the nitrogen level in Guichao2.IR38 has a strong regulation ability,which will quickly enhance nitrogen absorption and transport to increase the nitrogen concentration in the plant.Low nitrogen treatment significantly inhibits the expression of AMT1;2,Os NAR2.1,Os NRT1.1B,NRT2.3a in the root,but after 12 days of normal nitrogen recovery,the expression levels of Os NRT1.1A and Os NAR2.1 increased significantly in IR38.The above results indicate that Huanghuazhan is sensitive to low nitrogen,Guichao 2 is resistant to bottom nitrogen,IR38's strong regulation ability is closely related to the expression of genes related to nitrogen absorption and transport.Rice uptake and transport of nitrogen is the most critical step in nitrogen utilization,and it is also a prerequisite to use nitrogen.Similarly,Huanghuazhan and Guichao2 were insensitive to high nitrogen,and IR38 was relatively sensitive to high nitrogen,which were also closely related to nitrogen uptake and transport.In Huanghuazhan and Guichao2,high nitrogen can significantly inhibit the expression of nitrogen absorption and transportation related genes such as AMT1;2,Os NAR2.1,NRT2.3a,etc.,thereby inhibiting the absorption and transportation of nitrogen by roots.3.The soluble sugar and sucrose contents in leaf sheath did not change significantly after 12 days of high nitrogen treatment,but they were increased significantly after a period of time recovery of constant nitrogen,indicating that high nitrogen treatment could promote carbon metabolism of rice,but this effect would be delayed.Based on the above results,they can provide a certain theoretical basis for the nitrogen application management of Huanghuazhan,IR38 and Guichao2 in practice.Huang Huazhan is sensitive to low nitrogen and has a slow response to high nitrogen,so the nitrogen supply should be sufficient,but excessive nitrogen fertilizer is not necessary.Guichao2 is resistant to low and high nitrogen,so it can reduce the application of nitrogen properly and save cost in the production process.IR38 has a certain adaptability to the nitrogen-deficient environment and is more sensitive to high nitrogen.Therefore,in production practice,in order to obtain higher yield,you can achieve it by increasing the amount of nitrogen fertilizer.