Preliminary Study On Toxic And Metabolic Effects Of 2,3,4,5-tetrachlorobiphenyl And Its Derivatives In Rice(Oryza Sativa L.)

Organic pollutants widely distributed in the environment can be uptaken and biotransformed into various metabolites by plants,whose toxicities are higher than those of the parent compounds.In this thesis,2,3,4,5-tetrachlorobiphenyl(CB-61)was chosen as a kind of typical organic pollutant,and CB-61 and its hydroxylated and methoxylated derivatives,namely,4'-OH-CB-61 and 4'-MeO-CB-61,were separately exposed to rice(Oryza sative L.)to determine their phytotoxicity and metabolic responses.The main results of this thesis are summarized below:(1)CB-61,4'-OH-CB-61 and 4'-MeO-CB-61 induced growth inhibition and oxidative damage in rice seedlings,which ranked as follows:4'-MeO-CB-61>4'-OH-CB-61>CB-61.The biomasses of roots were decreased by 32.2%,56.6%and 64.3%at 500?g·L-1 of CB-61,4'-OH-CB-61 and 4'-MeO-CB-61,more significantly than those of shoots.With increasing concentrations of exposure chemicals(0-500?g·L-1),the activities of superoxide dismutase(SOD)and peroxidase(POD)in roots were decreased,while the malondialdehyde(MDA)contents reached maximum at 100 ?g·L-1 and then decreased.(2)4'-OH-CB-61 and 4'-MeO-CB-61 promoted the decomposition of saccharides and inhibited the synthesis of antioxidants in rice,showing a stronger metabolic disturbance than CB-61.In particular,exposure to 4'-MeO-CB-61 rose the energy demand,mainly manifested by the significant promotion of the pyruvate-centered catabolism such as pyruvate metabolism,the TCA cycle,the transfer of acetyl groups into mitochondria and the Warburg effect,and ultimately resulted in 14.2%-32.8%and 10.7%-38.6%decreases of sucrose and D-fructose,respectively.Meanwhile,synthesis of antioxidants(amino acids,phenols,phytosterols et al.)were promoted at varying levels in PCB-and OH-exposed group and detoxification mechanism mediated by glutathione was uniquely activated in rice after exposed to CB-61.The most effective antioxidant mechanism that rice coped with CB-61 explained the lowest phytotoxicity of CB-61 among the three chemicals.