| Rice is one of the most important crop plant in the world,it is crucial that enough yield of rice is produced.Nitrogen is one of the most important limiting factors in the process of food production,affects many aspects of growth and development of rice.Moreover,rice tillering is also an important factor determining the yield.The number of rice tillers is affected by many factors,in which nitrogen is one of the main factors.It is directive and practical to clearify and definite the relationship between nitrogen and rice tillering for creating the perfect plant type,improving nitrogen use efficiency and increasing the yield of rice.NIP?d3 and d10 was used as materials in thisstudy.By various experiment,including different nitrogen concentration(0,0.2,2.5,5 mM)or form(NH4NO3,(NH4)2SO4,Ca(NO3)2)hydroponics culture,the tiller number,enlongation changes,gene expression of different buds in NIP was measured.Tiller number and other physiological phenotypes,effect of GR24 teatment,nitrogen distribution by 15N labeling was detected in NIP?d3 and d10.Through above experiments,it revealed thatthe mechanism of nitrogen and strigolactone on rice tillering and other physiological phenomenon.The main results are listed as follows:1.Hydroponic experiments were conducted to study the effects of different nitrogen concentration,form and supply time on rice tiller under greenhouse condition.The results showed that NIP tiller number increased significantly compared with insufficient nitrogen,NH4+ did the work much better of the elongation of NIP tiller compared with NO3-,nitrogen couldn't effect the formation of tiller.2.Hydroponic experiments were conducted to study the effects of different nitrogen concentration on tiller activity.At 5 leaf stage(5L),the second(2nd)tiller bud of NIP and the fourth(4th)tiller bud at leaf blade base showed no obvious change,not stretched,but the third(3rd)tiller bud elongated significantly.This result suggested that,at the 5L stage,3rd tiller bud was in a dormant state under nitrogen relatively insufficiently.The 3rd tiller buds were analyzed under different nitrogen concentration.It showed that Histone H4 hybridyzation signals was strong,a mitotic S-phase marker gene,only under supplying nitrogen condition.And cell division related genes,including cdc2,CyclinD,cyclinB,PCNA,rPL34,rPL27,histone H2A,expression increased compared with depriving of nitrogen.In addition,it also found that expressions of strigolactone related genes D3,D10 and D14,d17,d27 genes were low in tiller bud without nitrogen.Above all,it illustrated that nitrogen controlled tillering elongation by cell division and strigolactone pathway.3.At 5 leaf stage(5L),the 3rd tiller buds were active or dormant respectively in different nitrogen concentration condition.The 3rd tiller buds were analyzed under different nitrogen concentration in this period.Comparing with 3L stage,it showed that 1881 genes of the junction of 5L stage were up-regulated and 2573 were down-regulated with nitrogen,2087 genes of the junction of 5L stage were up-regulated and 2410 were down-regulated with nitrogen All this indicated that nitrogen impacted rice growth and development remarkably.4.Tiller number of NIP,d3,d10,including other physiological phenotype,showed consistent changes with the nitrogen concentration through the different nitrogen hydroponic experiments,but the proportion of tiller number of NIP changed much more.It showed that nitrogen participated in the SLs regulation of rice tiller,and the relationship was not simple upstream and downstream.And nitrogen controlling tiller number coxuld have more ways.By GR24 treatment and 15N labeling experiment,allocation of nitrogenin different leaf of d3 and d10 changed significantly compared with NIP,especially the new N content of new leaves in d3 were much lower than NIP. |
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