Possible mediatory roles of heat acclimation and salicylic acid in protecting the sporophyte of marine macroalga Laminaria japonica(Phaeophyceae) from heat stress were studied.Heat stress resulted in oxidative injury ...Possible mediatory roles of heat acclimation and salicylic acid in protecting the sporophyte of marine macroalga Laminaria japonica(Phaeophyceae) from heat stress were studied.Heat stress resulted in oxidative injury in the kelp blades.Under heat stress significant accumulation of hydrogen peroxide(H_2O_2) and malonaldehyde(MDA),a membrane lipid peroxidation product,and a drastic decrease in chlorophyll a content were recorded.Activity of the enzymatic antioxidant system was drastically affected by heat stress.The activity of superoxide dismutase(SOD) was significantly increased while peroxidase(POD),catalase(CAT) and glutathione peroxidase(GPX) were greatly inhibited and,simultaneously,phenylalanine ammonia-lyase was activated while polyphenol oxidase(PPO) was inhibited.Both heat acclimation pretreatment and exogenous application of salicylic acid alleviated oxidative damage in kelp blades.Blades receiving heat acclimation pretreatment and exogenous salicylic acid prior to heat stress exhibited a reduced increase in H_2O_2 and MDA content,and a lower reduction in chlorophyll a content.Pretreatment with heat acclimation and salicylic acid elevated activities of SOD,POD,CAT,GPX and PPO.Considering these results collectively,we speculate that the inhibition of antioxidant enzymes is a possible cause of the heat-stress-induced oxidative stress in L.japonica,and enhanced thermotolerance may be associated,at least in part,with the elevated activity of the enzymatic antioxidant system.展开更多
The overvoltage phenomena of ultra high voltage (UHV) transmission lines are analyzed and verified by EMTDC/PSCAD simulation. Referring to the theoretical analyses and operating experiences of extra high voltage (EHV)...The overvoltage phenomena of ultra high voltage (UHV) transmission lines are analyzed and verified by EMTDC/PSCAD simulation. Referring to the theoretical analyses and operating experiences of extra high voltage (EHV) transmission lines in China and UHV transmission lines in Russia and Japan, the methods to suppress the internal overvoltage in UHV transmission lines by protection and control strategies are discussed. Through the cooperation among the recloser, shunt reactor, tripping and closing resistance, and metal oxide varistor(MOV), the overvoltage can be restrained within an acceptable level.展开更多
基金Supported by the Open Funds of the Key Oceanic Science and Engineering Laboratory of National Bureau of Oceanography(MESE-2008-01)the Specialized Research Program for Marine Public Welfare Industry,SOA(No.200805066)
文摘Possible mediatory roles of heat acclimation and salicylic acid in protecting the sporophyte of marine macroalga Laminaria japonica(Phaeophyceae) from heat stress were studied.Heat stress resulted in oxidative injury in the kelp blades.Under heat stress significant accumulation of hydrogen peroxide(H_2O_2) and malonaldehyde(MDA),a membrane lipid peroxidation product,and a drastic decrease in chlorophyll a content were recorded.Activity of the enzymatic antioxidant system was drastically affected by heat stress.The activity of superoxide dismutase(SOD) was significantly increased while peroxidase(POD),catalase(CAT) and glutathione peroxidase(GPX) were greatly inhibited and,simultaneously,phenylalanine ammonia-lyase was activated while polyphenol oxidase(PPO) was inhibited.Both heat acclimation pretreatment and exogenous application of salicylic acid alleviated oxidative damage in kelp blades.Blades receiving heat acclimation pretreatment and exogenous salicylic acid prior to heat stress exhibited a reduced increase in H_2O_2 and MDA content,and a lower reduction in chlorophyll a content.Pretreatment with heat acclimation and salicylic acid elevated activities of SOD,POD,CAT,GPX and PPO.Considering these results collectively,we speculate that the inhibition of antioxidant enzymes is a possible cause of the heat-stress-induced oxidative stress in L.japonica,and enhanced thermotolerance may be associated,at least in part,with the elevated activity of the enzymatic antioxidant system.
基金ABB (China) Research Ltd. and National Natural Science Foundation of China(No.50477037)
文摘The overvoltage phenomena of ultra high voltage (UHV) transmission lines are analyzed and verified by EMTDC/PSCAD simulation. Referring to the theoretical analyses and operating experiences of extra high voltage (EHV) transmission lines in China and UHV transmission lines in Russia and Japan, the methods to suppress the internal overvoltage in UHV transmission lines by protection and control strategies are discussed. Through the cooperation among the recloser, shunt reactor, tripping and closing resistance, and metal oxide varistor(MOV), the overvoltage can be restrained within an acceptable level.
