title: The effect of excess Zn on mineral nutrition and antioxidative response in rapeseed seedlings.
abstract: Zinc (Zn) is a necessary element for plants, but excess Zn can be detrimental. To investigate Zn toxicity, rapeseed (Brassica napus) seedlings were treated with 0.07-1.12 mM Zn for 7d. Inhibition of plant growth along with root damage, chlorosis and decreased chlorophyll (a and b) content in newly expanded leaves (the second and third leaves formed following cotyledons) were found under Zn stress. The Zn content increased in plants under external Zn stress, while concentrations of phosphorus, copper, iron, manganese and magnesium reduced significantly, especially in roots. Meanwhile, increased lipid peroxidation was detected biochemically and histochemically. Compared with controls, NADH oxidase and peroxidase (POD) activity increased in leaves and roots of plants under high Zn, but superoxide dismutase (SOD), catalase and ascorbate peroxidase activities decreased. The changes in glutathione S-transferase activity and in ascorbic acid, dehydroascorbate, non-protein thiols and glutathione contents were also measured under Zn stress. Isoforms of SOD and POD were separated using non-denaturing polyacrylamide gel electrophoresis and their activities were analyzed. Our results suggested that excess Zn exerts its toxicity partially through disturbing nutrient balance and inducing oxidative stress in plants. These data will be helpful for better understanding of toxicity of Zn and the adaptive mechanism in Zn non-hyperaccumulator plants.
authors.affiliation: Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Ministry of Education, College of Environmental Science and Engineering, Hohai University, Nanjing 210098, China.
authors.forename: Chao
authors.initials: C
authors.lastname: Wang
authors.forename: Song He
authors.initials: SH
authors.lastname: Zhang
authors.forename: Pei Fang
authors.initials: PF
authors.lastname: Wang
authors.forename: Jun
authors.initials: J
authors.lastname: Hou
authors.forename: Wen Jing
authors.initials: WJ
authors.lastname: Zhang
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.forename: Zhi Ping
authors.initials: ZP
authors.lastname: Lin