| Acid rain and high temperature(HT)are foremost environmental problems affecting plant growth and development,especially in central and southern China.Cinnamomum camphora grows in the south of China,unavoidably undergoes acid rain and following HT.To uncover their effects on the plant growth,the reactive oxygen species(ROS)metabolism,pigment content and Chl fluorescence were investigated under simulated acid rain(Si AR),HT and their dual stresses.(1)Si AR treatment promoted ROS production and lipid peroxidation in C.camphora,whether the plants were further kept at normal temperature(28 ?)or under HT stress(40 ?).HT stress after Si AR aggravated the promotion.(2)The activities of enzymatic antioxidants including superoxide dismutase,peroxidase,catalase,ascorbate(As A)peroxidase,monodehydroascorbate reductase,dehydroascorbate reductase,and glutathione(GSH)reductase increased under single HT stress but decreased under Si AR stress at p H2.5.However,their activities declined under HT after Si AR at p H 3.5,indicating that HT after Si AR promoted the enzyme inactivation.Meanwhile,HT stress after Si AR treatment further decreased the content of non-enzymatic antioxidants,including As A,GSH and carotenoids.(3)The photosynthetic abilities in C.camphora declined under single Si AR and HT stress,but HT after Si AR stress aggravated the decrease,due to the enhanced effects on the reduction of photosynthetic pigment content,inhibition on quantum production and electron transport in PSII,as well as dissipation of absorbed light energy as heat.It can be deduced that the initial acid rain cannot enhance C.camphora tolerance to the following HT,as HT stress aggravated the production of ROS and the inhibition of photosynthetic abilities.Lowering p H of Si AR pretreatment enhanced the damage to the plants under the following HT stress,indicating that the impacts of the two stresses in natural conditions on the species should depend on the p H of initial acid rain. |
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