High light accelerated tobacco leaf senescence:changes in H_2O_2 metabolism and enzyme activities
The possible role of H2O2 metabolism in high light-regulated senescence of tobacco(Nicotiana rustica L.,Gansu yellow flower) leaves was investigated.High light(PFD 630 μmol·m-2·s-1) accelerated leaf senescence with higher protein and chlorophyll decrease rates but at the same time caused more H2O2 accumulation than that of normal light(PFD 270 μmol·m-2·s-1).High light treatment resulted in distinct lower catalase and ascorbate peroxidase activities and higher superoxide dismutase activities than that of normal light after leaf reached full expansion.Leaf peroxidase activities kept rising under high light until the oldest leaf.The results obtained suggest that the accelerated leaf senescence by high light is closely related to the changed H2O2 metabolism by catalase and ascorbate peroxidase and superoxide dismutase after leaf reached full expansion.