Effects Of Water And Nitrogen Regulation On Accumulation And Transport Of Non-structural Carbohydrates And Spikelets Formation In Rice

As an important energy substance,non-structural carbohydrate is involved in young spike development and spikelets formation.Water and nitrogen play important roles in the growth and development of young panicles and spikelets formation.However,the mechanism of nitrogen regulation on spikelet differentiation and degradation has not been fully elucidated,and the response of assimilate movement and spikelet formation to the coupling of water and nitrogen is still lacking in systematic studies.In experiment 1,three nitrogen application levels(N1:105,N2:210,N3:315 kg·hm-2)were set with large-panicle hybrid rice Zhejingyou 1758 and conventional japonica rice Suxiangjing 100 as materials to investigate the effects of nitrogen application on the accumulation and distribution of NSC and spiket formation in rice.In experiment 2,the large-panicle hybrid japonica rice Yongyou 1540 was used as the material,and irrigation mode was set(W0:shallow water layer irrigation;W1:alternate dry and wet irrigation)and nitrogen fertilizer operation(under the condition of 270 kg·hm-2 nitrogen application,the ratio of base tillering fertilizer to ear fertilizer was N 1:3:7;N2:5:5;N3:7:3)two-factor experiment was conducted to analyze the response of different agronomic and physiological traits as well as spikelet formation to irrigation coupled nitrogen fertilizer operation.By setting the above different cultivation methods,this study studied the accumulation and distribution of NSC under different nitrogen levels,as well as the differences in the differentiation and degradation of branchlets and spikelets at different parts of rice panicle,further explored the relationship between NSC metabolism and branchlets and spikelets differentiation and degradation,and explored the best water-nitrogen coupling management measures to provide theoretical and technical support for high-yield cultivation of rice.The main research results are as follows:1.Nitrogen application rate affected the concentration and accumulation of NSC in stem sheath,leaf and young ear of two different panicle varieties at spike differentiation stage,and the concentration and content of NSC in stem sheath at heading stage were significantly higher than those in young ear and leaf.Medium nitrogen application rate N2 treatment was beneficial to increase the accumulation of NSC in stem sheath before flowering and promote the transfer of NSC to grain after flowering,which laid the material foundation for high yield.Compared with N1 and N3,N2 treatment had the highest total number of branches and stems,the number of differentiation and the number of spikelets,while the number of degradation and the rate of degradation were the lowest.N2 treatment significantly increased the number of secondary spikelets in middle and lower secondary spikelets and decreased the number of degradation,and promoted the formation of middle and lower secondary spikelets and spikelets.The trends of the two cultivars were consistent.Correlation analysis showed that higher NSC storage in stem sheath 20,10 d before heading was not conducive to the differentiation of young panicles,branches and spikelet,on the contrary,would increase the degradation of the two japonica rice varieties.However,the accumulation of NSC in young panicles 15,5 d before heading was significantly positively correlated with the differentiation number of branches and spikelet and the existing number,and significantly negatively correlated with the degradation number.It is the key period to determine the number of grains per spike.2.There was significant interaction effect between irrigation mode and nitrogen fertilizer operation on rice yield.Under the same nitrogen fertilizer treatment,W1 significantly increased the number of grains per panicle,seed setting rate and 1000-grain weight,and thus increased the yield.N2 could significantly increase the yield under the same irrigation method,and the main reason for the increase of yield was the increase of seed setting rate and 1000grain weight.Compared with W0,W1 significantly increased tillering rate,dry matter accumulation in overshoot and NSC transfer and transport efficiency in stem sheath under each nitrogen fertilizer ratio.Promote the synthesis of Z+ZR,IAA and ABA in young ears during ear differentiation;Enhance the activities of AGP,SPS and α-amylase in stem sheath and young panicle,promote the redistribution and redistribution of assimilated substances,and increase the contribution rate of stem sheath stored substances to yield.Irrigation and nitrogen fertilization had no significant effects on the differentiation number of primary stem and spikelet,but had significant effects on the degradation number of secondary stem and spikelet.W1 significantly increased the number of total branchlets and spikelets and the number of existing spikelets.Under the three nitrogen treatments,the number of total stem and spikelet differentiation and extant number of N2 was the highest,while the number of degenerated number was the lowest.Among all treatments,light dry and wet alternate irrigation(W1)combined with nitrogen fertilizer operation 5:5(N2)could effectively construct reasonable population,coordinate source-pool relationship,increase spikelet number per panicle and yield significantly,which was the optimal water and nitrogen operation mode under the experimental conditions.