Study On Regulation Mechanism Of Floral Bud Differentiation In Canola

Reproductive growth and vegetative growth are two phases of plant's life.The plant transformation from reproductive growth to vegetative growth,superficially,is a process of flowering.Actually floral bud differentiation is the symbol of this transformation. During this transformation,variation of DNA methylation level and the influencing factors are one of the central issues on which many researches are being carried in recent years.The experiment was conducted both in field and laboratory,studying the effect on floral bud differentiation DNA methylation level of stem point,soluble protein contents and soluble sugar contents of leaves by adopting Zhongyouza No.11 as the trail materials. The treatments included applying low temperature,GA₃ and PP₃₃₃ to canola seedling;and applying 5-azaC alone,5-azaC and low temperature to germinating seeds.The experiment was supposed to explore the adjustment mechanism of floral bud differentiation,and supply theoretical basis to practical production.The results showed:1.Greenery number of canola seedling and leaf age was correlated to index of floral bud differentiation linear positive.At Wuhan,middle ten days of October,under the condition of direct seeding,when greenery number was 5.89,leaf age was 7.50,it was floral bud differentiation of canola that began.2.Low temperature could impetus floral bud differentiation,and the longer of treatment it takes,the more obvious the effect was.Except canola seedling,germinating seeds which accepted 10 days low temperature began to floral bud differentiation in advance.Treatment of applying 0μmol/L 5-azaC on germinating seeds promoted differentiation,but 250 and 500μmol/L 5-azaC suppressed.Low temperature and 50μmol/L 5-azaC applying on germinating seeds also could promote the differentiation, but low temperature and high concentrations of 5-azaC(250,500μmol/L) suppressed. The promotion effect of low concentrations of 5-azaC could enhanced by low temperature,what was called additive effect.Low temperature could partly help to relieve the suppression of high concentrations of 5-azaC.Applying GA₃ to canola seedline could impetus floral bud differentiation,the higher the concentrations was,the more obviously the suppression effect was.Treatment of applying PP₃₃₃ to canola seedling restrained floral bud differentiation.GA₃ and PP₃₃₃ may impact the differentiation through increase or decrease the GA contents of plant.3.Low temperature reduced DNA methylation level of stem point,the treatment stayed longer,the decrement of DNA methylation level was more.DNA methylation level of germinating seeds decreased,exposed to low temperature 10 days.But seedling was more likely affect by low temperature than seeds.Application 5-azaC of 50μmol/L and 250μmol/L on germinating seeds could decline DNA methylation level.With increasing concentrations of 5-azaC,DNA methylation level was firstly being up,then went down.Low temperature and 5-azaC had an additive effect on decreasing DNA methylation level.That indicated low temperature may impetus floral bud differentiation by decreasing DNA methylation level.There was no influence of GA₃(100,300, 500mg/L) and PP₃₃₃(100,200,400mg/L) on DNA methylation level of stem point.That illustrated controlling DNA methylation level was not the way of GA₃ and PP₃₃₃ to adjust floral bud differentiation.The trend of DNA methylation level of all treatments,after floral bud differentiation,was being down.4.Soluble protein contents was increased by low temperature.With the treat time prolonging,soluble protein contents increased at first and declined later.5-azaC and 5-azaC and low temperature to germinating seeds,GA₃ and PP₃₃₃ to seedling did not influence soluble protein contents.After floral bud differentiation,the trend of soluble protein contents was being up,and of DNA methylation level was being down.That indicated the decrement of DNA methylation level made more gene express,so soluble protein contents increased corresponding.5.Soluble sugar contents of seedling increased,with 12 days low temperature treatment.With the treat time prolonging,soluble sugar contents increased firstly,then went down.5-azaC to germinating seeds and GA₃ to seedling had hardly impact on soluble sugar contents.Low temperature and 5-azaC(500μmol/L) to germinating seeds decreased soluble sugar contents.With increasing concentrations of 5-azaC(100,300, 500μmol/L),soluble sugar contents decreased.Soluble sugar contents went down after floral bud differentiation,indicating that after transformation from reproductive growth to vegetative growth,large amount of soluble sugar contents were used to produce protein or something like that,in order to form some new organs.