| Rice yield is mainly composed of the number of spikelets per panicle,the number of panicles per unit area,the seed setting rate,and the thousand-grain weight.However,the amount of nitrogen(N)and transplanting density are two important cultivation measures that affect these factors.How to improve the efficiency of N use and increase suitable planting density to achieve the purpose of increasing yield is a research hotspot in current agricultural production.While studying high-yield cultivation techniques,studying the regulation of genes related to panicle type has important guiding significance for further stimulating rice production potential.Among them,large panicle varieties have strong photosynthetic capacity,N absorption capacity,and large amount of bioaccumulation at various stages,etc.This characteristic is an ideal variety that is conducive to the increase in yield.Improving the panicle type and plant type by digging out the excellent genes of rice also provides new ideas for further increasing the current rice yield:By changing the gene expression level to obtain materials of different panicle types,it is helpful to study the effects of N application rate and transplanting density on the growth and development,yield formation,panicle composition and nutrient element absorption and utilization efficiency of different rice panicle type.In this study,the japonica rice variety Nipponbare was used as the wild type,and two overexpression lines of the OsERF2 gene were constructed using it as the recipient as the test materials.By studying the interaction of transplanting density,N application rate,and ERF2 expression level,the growth and development of rice.Yield formation and the effects of nitrogen(N),phosphorus(P)and potassium(K)absorption,in order to understand the regulation mechanism of ERF2 expression level on rice panicle type and seek optimal cultivation measures.The main findings are as follows:1.Panicle typeWith the increase of N application rate,the number of primary branches and secondary branches of wild-type and overexpression materials increased;with the increase of ERF2 expression level,the length of wild-type panicle,the number of primary branches,the number of secondary branches,the number of primary branch spikes and the number of secondary branch spikes can be significantly increased.2.Dry matter productionApplying N fertilizer and increasing the expression level of ERF2 can increase the leaf area index;with the increase of N application,the grain-to-leaf ratio of the wild type will show a downward trend,while the increase of the expression level of ERF2 can significantly increase the grain-to-leaf ratio of rice and improve the source-sink relationship:applying N fertilizer and increasing the expression level of ERF2 can significantly increase the bioaccumulation of the above-ground tissues at the maturity and heading stages of rice;increasing the transplanting density will significantly increase the bioaccumulation of the above-ground rice at the heading and maturity stages.3.Yield and its componentsWith the increase of N application rate,the number of panicles per unit area gradually increases,yield and N application rate show a parabolic relationship with the opening facing down;Increasing transplanting density will significantly increase the number of panicles per unit area and increase rice yield;The increase in the expression level of ERF2 significantly increased the yield of rice,and the yield of overexpression materials was small,especially under the treatment of high-density and the yield decreased,which may be mainly related to the low seed setting rate.With the increase of N application rate,the seed setting rate showed a trend of first increasing and then decreasing,and the thousand-grain weight showed a decreasing trend.Especially,it has a greater impact on the thousand-grain weight and seed setting rate of primary branchs,the number of spikelets per panicle shows a trend of increasing first and then decreasing.With the increase of transplanting density,the number of spikelets per panicle of overexpression materials decreased slightly,and the wild type increased slightly;with the increase of ERF2 expression level,the number of spikelets per panicle also increased significantly.4.N absorption and utilizationAt the heading stage of rice,the amount of N uptake by each tissue basically increases with the increase in the amount of N applied.The response degree of each tissue to N fertilizer is leaf>stem>panicle;The effect of density on the N uptake of the leaves and above ground at the heading stage of rice has also reached a significant level,increasing the transplanting density is beneficial to increase the N accumulation in the leaves;Increasing the expression level of ERF2 is beneficial to promote the absorption of N fertilizer by the rice stems at the heading stage,thereby increasing the N accumulation.The effect of N fertilizer on the N uptake of various tissues in rice maturity has reached a very significant level.With the increase in the amount of N applied,the amount of N uptake by the tissues also continues to increase;Increasing the transplanting density is beneficial to increase the N uptake of various tissues in the mature stage;Increasing the expression level of ERF2 is beneficial to increase the N uptake of rice tissues,especially in the OX1 material,the increasing trend is more obvious.N application rate significantly affects N use efficiency for biomass production and N use efficiency for grain output,With the increase of N application rate,N use efficiency for biomass production and N use efficiency for grain output gradually decrease;The N use efficiency for grain output of the overexpression material is greater than that of the wild type under multiple N fertilizer treatments;the increase of ERF2 expression level is beneficial to increase the N use efficiency for grain output of rice.With the increase of N application rate,the N physiological efficiency,N utilization efficiency,N agronomy efficiency and N partial factor productivity all decreased;When the transplanting density increases,the N physiological efficiency and N partial factor productivity of the overexpression materials are all greater than that of the wild type;Under low-density treatment,the utilization agronomy efficiency of overexpression material is lower than that of wild type.5.Absorption and utilization of P、K、Ca、Mg、SBoth the application of N fertilizer and the increase of transplanting density can significantly increase the P uptake of rice stems,panicles,leaves and aboveground parts;The increase in transplanting density also significantly increased the absorption of P by rice;the increase of ERF2 expression level is beneficial to increase P uptake of different parts of rice at maturity stage,especially the amount of P uptake by stems and panicles.With the increase of N application rate,the P transport amount of stems,sheaths,leaves and the increase of panicles P all showed a trend of first increasing and then decreasing;Under the two density treatments,the amount of overexpression material P transported in the stems,sheaths,leaves and the increased amount of P in panicles are greater than that of the wild type.With the increase of N application rate,the K uptake of rice stems will be reduced,but will increase the K uptake of panicles and leaves;The effect of ERF2 expression level on leaves K uptake is regulated by density;The K uptake of the stems,panicles and aboveground parts of the overexpression materials is greater than that of the wild type.The application of N fertilizer will reduce the K transport of stems,sheaths and leaves in some treatments,improve the increase of K in the panicles,the production efficiency of K dry matter and the production efficiency of K in rice;The effect of density on the K transport of stems,sheaths and leaves reaches a significant level;the increase in the expression level of ERF2 is beneficial to increase the efficiency of K dry matter production in rice and the production efficiency of grain in rice.Changes in transplanting density and ERF2 expression level will cause changes in the proportion of P、K、Ca、Mg、S in various parts of rice.With the increase of transplanting density,the correlation between the N content rate and P content rate of the stem of wild-type and overexpression materials at the heading and maturity stages decreased,the correlation between leaf N content rate and Mg content rate under the two density treatments reached a very significant level.There is a significant or extremely significant negative correlation between the N content rate and Ca content rate of each part of the wild-type at the mature stage,when the density increases,the correlation is not significant,and the increase in the expression level of ERF2 will cause its correlation to be significantly reduced.Due to the significant changes in the correlation between the nitrogen content and calcium content of the three materials at the heading stage and the mature stage,ERF2 may have a certain influence on the absorption of calcium from the heading stage to the mature stage. |
