Biochemical Mechanism of Synergistic Senescence between Root System and Flag Leaf in Broomcorn Millet(Panicum miliaceum L.)

Bio-chemical mechanism of synergistic senescence between root and flag leaf in broomcorn millet was studied with 'Yumi 3' employed as the experiment material.The investigation of root,growth index,protective enzyme activities,soluble protein contents from the jointing stage to maturing stage.The results showed that from the jointing stage to maturing stage the root vigor,root surface areas,root dry matters,leaf areas and flag leaf dry matters,the superoxide dismutase(SOD),catalase(CAT),and peroxidase(POD)activities of root and flag leaf initially increased from low to high and then declined.The soluble protein contents of root and flag leaf gradually declined;The results indicated that dry matter accumulation and allocation to all organs were maximum in 34~41 d after jointing(in the earlier period and middle of grain filling).The content of MDA gradually increased.The flag leaf SOD,CAT,POD protective enzymes activities,soluble protein contents were significantly higher than that of root the corresponding period,and the content of MDA significantly less than that of root the corresponding period.The results indicated that hindered carbohydrate was transfered from the flag leaf and the root during late stage.Moreover,the activities of oxygen protective enzyme in flag leaf and root gradually declined.The ability of reactive oxygen species metabolism was declined slowly.The reactive oxygen species accumulated in cell and resulted in its lipid membrane damage during the aging process.Therefore,improving rhizosphere nutrition and raising root vigor help delay leaf senescence.In the aging process,the relationship between root senescence and anti-oxygen enzyme activities was weaker than that in flag leaf.