Variation Characteristics Of Flavonoids In Blueberry Leaves During Color Changes In Autumns

The variation characterization of the contents,compositions and ratios of the anthocyanins and chlorophylls were explicited to investigate the color changing mechanism of 'Northland' blueberry(Vaccinium corymbosum L.)leaves in autumn.On this basis,the flavonoids changing mechanism of color changing leaves in autumn were studied combining with the change of soluble sugars.In addition,Characteristics of relative indexes in leaves of different parts of new shoots were investigated to give full play to and improve the economic use value and ornamental value of blueberry leaves.,The results showed that:4 kinds of anthocyanin aglycones were detected in 'Northland' leaves:delphinidin,petunidin,malvidin and cyanidin,on which delphinidin and petunidin accounted for the largest contents,accounting for about 88%of the total anthocyanin content.Their contents increased with the leaf color change but the ratio constant,about 0.85.5 kinds of anthocyanin compositions were tested in green leaves.The compositions tested increased with leaf color change.11 kinds of anthocyanin compositions were tested in red leaves,including delphinidin-3-O-arabinoside,petunidin-3-O-galactose and petunidin-3-O-glucoside,which taking a proportion up to 90%.With the change of leaf color,the total contents of anthocyanin increased,and the content of proanthocyanidins decreased,and the content of flavonol increased slightly.In addition,anthocyanin began to rise significantly from the change of color S3 phase(red and green taken equivalent areas)while proanthocyanidins decreased significantly at S1-S2 stage(when leaves began to turn red).Total flavonoids contents in the red leaves were close to the green leaves.The anthocyanins and flavonols in the red leaves were increased 9 times and 30%respectively.But the proanthocyanidins contents were decreased 20%.The chlorophylls decreased about 50%.The total soluble sugar,fructose,glucose and sucrose contents in the red leaves were increaces 20%-40%,respectively,in which sucrose accounted for the highest proportion of total soluble sugars contents(about 60%).The leaf pigments and flavonoids in lower parts of new shoots were significangly higher than the upper and middle parts.The flavonoids in the basal leaves changed most during leaf color change,while the chlorophyll content in the middle leaves was the largest.There were significant correlations between temperature and chlorophyll,soluble sugar,total flavonoids.The change of chlorophylls contents were significantly related to flavonoids.Fructose were positive significantly related to anthocyanins and flavonols.Sucrose were negatively related to them.The proanthocyanidins were rich in the palisade tissues,spongy tissues,phloem and pith rays;while the flavonols were rich in the palisade tissues,vascular bundle sheath cellss,xylem,pith rays,collenchyma and epidermal cells,but less in the parenchyma and spongy tissues.According to the comprehensive analysis,the increase of anthocyanins and the decrease of chlorophylls contents were key factors of leaf color changing.Delphinidin and petunidin were main anthocyanins that affected the color changing process.Flavonols tended to be distributed in tissues that were high in photosynthesis,and proanthocyanidins were distributed uniformly in the mesophyll cells.