The Research Of Panicle Fertilizer And 6-BA In Panicle Differentiation Stage On Spikelets Forming And Study On Its Mechanism

Increasing spikelet number per panicle is one of the key factors for high yield,and panicle differentiation is the important stage for spikelet number formation.In this research, we employ indica rice cultivation(Yangdao 6) to explore the development characteristic of panicle differentiation regulated by panicle fertilizer and cytokinin-like hormone 6-BA (6-benzyl adenine) in pot experiment.Researched young panicle growth,SPAD values changes curve of top leaves,and the expression pattern of cytokinin oxidase/dehydrogenase (OsCKX2),RFL,RAP1 during panicle differentiation stage in rice,illustrate that effect nitrogen fertilizer and 6-BA applied on spikelets number formation.Results showed as following:1.The change tendency of panicle fresh weight and length is "S" during the whole younger panicle initiation stage.The panicles grow slowly prophase,but grow fast markedly from spike differentiation,especially during meiosis phase stage,panicle weight increase draped behind panicle length.Making use of panicle fertilizer could delay the time of branch and spikelet differentiation,this is the foundation of forming lots of spikelets, 6-BA accelerates panicle differentiation.With use of panicle fertilizer or 6-BA,any of them can accelerates the development of the length and weight of panicle,produces more room and assimilatory matter for differentiated spikelets.It is remarkable that the increase of panicle length and weight in the treatment of both of them,and the number of spikelet each panicle is more than 450.Suggesting the use of panicle fertilizer and 6-BA is beneficial for the panicle development and enhancing the number of spikelets.2.Panicle fertilizer effects the length and width development of top three leaves remarkably,but has little influence on the reciprocal fourth leaf.The effect of 6-BA on leaves development is almost void,just useful of the reciprocal fourth leaf length,it means making use of them can improve the area of rice accepted light.The SPAD values of functional leaves increased with use of panicle fertilizer and 6-BA during panicle development,at the time of heading,compared to NOB0 treatment,the SPAD values of top three leaves improved about 1/3 with N fertilizer treatments,this implies rice leaves photosynthesis enhanced.6-BA just affects the shoot out leaves when 6-BA was applied.3.Applied panicle fertilizer and 6-BA can accelerate the spikelets differentiation, increase fecundity rate of the second branch and spikelets,the final spikelets number of per panicle is 264.3 in NHBH treatment,and the fecundity rate increased 121.1%compared with NOB0 treatments.But the degraded rate of spikelets is more than NOB0 treatment in other treatments,suppose it's the reason that the assimilation substance is not enough supplied to panicle during the meiosis stage.It's a key step to forming heavy panicle that making more assimilation substance during this stage.4.According to the results of RT-PCR,the expression of OsCKX2(cytokinin oxidase/ dehydrogenase) is affected by panicle fertilizer and 6-BA,the panicle fertilizer can delay its expression; and 6-BA induces its expression ahead,but the expression level is reduced.These results indicate that the reduced expression level of OsCKX2 in inflorescence meristems conducs the accumulation of cytokinin in young panicle,and this results in larger number of spikelets per panicle.5.The expression level of RFL is weak at the panicle differentiation initiation,and becomes higher during organ forming stage,but don't be detected during pollen full filling stage.The RAP1 maintains the same expression level alonging with whole panicle differentiation process.According our research,panicle fertilizer and 6-BA have no effect on their expression,that means the two genes can't regulate the inflorence differentiation of rice,and don't affect the number of grain per panicle...