Leaf senescence and activities of antioxidant enzymes in different broomcorn millet (Panicum miliaceum L.) cultivars under simulated drought condition

Drought is a major stress which leads to reduction in crop yield. In this study, three broomcorn millet varieties, namely Ningmi 13, Neimi 5 and Jinmi 4, were planted. Chlorophyll contents, superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) activities, malondialdehyde (MDA) and superoxide anion (O 2 -. ) contents were investigated from flowering to maturing stage under water deficit. The results showed that the chlorophyll contents, SOD, CAT and POD activities gradually decreased, 14 d after anthesis, while MDA and O 2 -. contents gradually increased as leaves senescenced. Although leaves of these varieties presented a similar tendency in their senescence that their functional leaves aged gradually from bottom to top, the differences of aging process existed among three varieties. Compared with Neimi 5 and Jinmi 4, the leaves of Ningmi 13 showed slow decline in chlorophyll content, SOD and CAT activities, fast decline in POD activity and slow increase in MDA and O 2 -. content, thus, prolonging their function duration and slowing down the senescence of leaves, which is conductive to the accumulation of photosynthates. Chlorophyll content, SOD and CAT activities had positive correlation with seed yield, but POD, MDA and O 2 -. content had negative correlation with seed yield under drought condition. In broomcorn millet, leaf aging and physiological and biochemical mechanisms vary depending on the genotypes. SOD probably was involved in leaf-aging regulation and synergistically alleviates the damage of reactive oxygen, so as to prolong the functional period of the leaves, ultimately improving the yield.