| Panicle N fertilizer,that is nitrogen fertilizer applied at panicle development stage,has great influence on the development of rice panicle.Studies have revealed that the beneficial response of nitrogen fertilizer on spikelet development is associated with the increase of spikelets number per panicle.However,little is known concerning the effect of panicle N fertilizer on endogenous hormones in rice young panicle.In the present study,two japonica rice cultivars(Wuyujing 3 and 2401) were used,and two panicle N fertilizer treatments, 120 kg N ha-1 as high nitrogen(HN) and 0 kg N ha1 as low nitrogen(LN),were conducted.1.Wuyujing 3 and 2401 were used to investigate the relationship between spikelets number and hormonal changes during rice panicle differentiation.The results showed that zeatin + zeatin riboside(ZRs),isopen-tenyl adenine(iPAs),indole-3-acetic acid(IAA),and abscisic acid(ABA) concentrations were the highest at spikelet differentiation stage,then declined and remained almost static before heading,and recovered slightly afterward. Differently,gibberellin(GAs) concentration was lowly all the while,but it had a sharply increase after heading.Panicle N fertilizer treatment resulted in higher concentrations of ZRs and iPAs,especially at the spikelet differentiation stage.By the contrary,panicle N fertilizer decreased the concentration of ABA.Whereas,IAA displayed lower concentration in I-IN as compared to LN.Moreover,there were higher ratios of ZRs/IAA and iPAs/IAA for HN as compared to LN during the panicle differentiation stage.The difference between them was the maximum at the spikelet differentiation stage and then declined to the minimum before heading.Moreover,Panicle N fertilizer treatment had a lower concentration of ABA,while,there was no significant difference between two treatments on the concentration of GAs.The results suggested that the effect of panicle N fertilizer on spikelet differentiation and numbers per panicle could be associated with the changes of endogenous hormones,either in their concentrations or in their ratios.2.2401 was used,and two panicle N fertilizer treatments were conducted to analyze the endogenous hormones of the top 4 leaves and sheaths at the spikelet differentiation stage.Zeatin+zeatin riboside(ZRs),isopen-tenyl adenine(iPAs),indole-3-acetic acid (IAA),abscisic acid(ABA),and gibberellin(GAs) were analyzed in this experiment.The results showed as follows,the concentrations of the hormones we have checked in high nitrogen treatments were notably higher than that in low nitrogen treatments.During the stage of spikelet differentiation,the trend of the concentration variation of hormones from top 1st to 4th leaves was similar as that from top 1st to 4th sheaths,while,higher hormonal concentration was detected in leaves than in sheaths.From top 1st to 4th leaves and sheaths, the concentrations of iPAs and GAs decreased;The concentrations of ZRs and IAA had a complex variation that the top 2nd leaves and sheaths of low nitrogen treatment and the top 3rd leaves and sheaths of high nitrogen treatment had the highest hormonal concentration; The concentration of ABA increased from top 1st to 3rd leaves and dropped in top 4th leaves,while it kept on increasing from top 1st to 4th sheaths.The results have revealed that:(1) Panicle N fertilizer enhanced the hormonal concentrations of leaves and sheaths of rice whether growth-promoting hormones,or growth-restraining hormones;(2) The concentration variation of ZRs and iPAs from top 1st to 4th leaves and sheaths had different trend,it probably because of that they were synthesized in different tissues;(3) It is probably that,endogenic hormones affected the growth and consenescence of trophic organization mostly by their balance.3.Wuyujing 3 was used to study the effects of nitric oxide(NO) on rice panicle development by inject NO donor(SNP) and scavenger(PTIO) during the later period of primary branch differentiation stage.The results showed that,the treatment by injected 50μmol·L-1 SNP has a higher number of secondary branch and spikelet,while the treatment of PTIO has a lower number of that.Otherwise,Cytokinin of zeatin+zeatin riboside(ZRs) and isopen-tenyl adenine(iPAs) were analyzed in this experiment.We find that the concentrations of ZRs and iPAs in young panicle by injected SNP were higher during spikelet differentiation stage.It is probably that,there are some relationships between NO and Cytokinin.
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