Leaf senescence and reactive oxygen species metabolism of broomcorn millet (Panicum miliaceum L.) under drought condition

From anthesis to mature stage, changes in the contents of chlorophyll and soluble protein, malondialdehyde (MDA) and the activities of antioxidative enzymes: superoxide dismutase (SOD, EC1.15.1.1), catalase (CAT, EC 1.11.1.6) and peroxidase (POD, EC 1.11.1.7) in the leaves of three broomcorn millet varieties (Ning-Mi 13, Nei-Mi 5 and Yu-Mi 3) were studied. The results showed that the contents of chlorophyll and soluble protein and the activities of SOD, CAT and POD in leaves of three broomcorn millet varieties rose and then declined with the progression of leaf senescence, the content of activities of antioxidative enzymes of flag leaf was high and declined slowly, and the content of MDA was low and rose gradually with senescence. Although the leaves of the three varieties generally presented a similar tendency in their senescence, their senescence progresses significantly differed. Among the varieties, the activities of SOD, CAT and POD reduced slowly in Ning-Mi 13, followed by Nei-Mi 5 and Yu-Mi 3. These changes were observed significantly in the middle and late stage of grain filling. Taken together, the results implicated a vitally important role played by leaf senescence alleviation in promoting grain filling and enhancing the yield and quality of Ning-Mi 13 in the rain-fed agriculture area.