| With the continuous progress of human society, heavy metal pollution becomesvery serious environmental problems in the world. Heavy metals have characteristics ofeasy spreading, difficulty of breaking down, toxic and easy bioaccumulation. It is animportant factor of environmental pollution. It has brought great harm to lives anddevelopment of human.Isoetes sinensis is Lobular type ferns, mire indicating Isoetes plants of Isoetaceae.It has been endangered species due to the change of the living environment and habitatloss, which has been listed as national key protected wild plants. Researching changesof I.sinensis was called “living fossil plant” in adversity especially heavy metal stresswhich contributes to reveal the original reaction mechanism of plant under stress.The test was used two kinds of heavy metals Pb and Cd on I.sinensis. Heavymetals were in the form of Pb(NO3)2and CdCl2solution. The test set threeconcentrations of each heavy metal. Three concentrations of Pb were500mg·L-1(Pb-l),2000mg·L-1(Pb-2) and5000mg·L-1(Pb-3). Three concentrations of Cd were100mg·L-1(Cd-1),250mg·L-1(Cd-2) and500mg·L-1(Cd-3). It was selected leaves distancerhizome4to8cm in the fourteenth days under stress treatment to determine SOD, POD,CAT activities and MDA contents for researching heavy metal stress reaction ofI.sinensis antioxidant enzyme system.We determined the degree of DNA methylation with MSAP (methylation-sensitiveamplified polymorphism) technology for researching I.sinensis response mechanism ofheavy metal in aspect of gene expression and regulation. The test results showed that:1. Heavy metal Pb, Cd stress had significant influence on I.sinensis SOD, POD,CAT activities and MDA contents. Pb stress, SOD and POD activities were significantlylower than the control, and the lowest were under2000mg·L-1stress. CAT activitieswere all higher than the control, and the highest was under500mg·L-1stress. Thecontents of MDA increased gradually with the concentration, and was significantlyhigher than the control under5000mg·L-1stress. Cd stress, the changes of SODactivities were the same to Pb stress. Although POD activities were significantly lowerthan the control, the activity was higher than the other two concentrations under250mg·L-1stress. CAT activity was lower than the control under500mg·L-1stress, and activities were higher than the control under100mg·L-1and250mg·L-1stress. Amongthem, CAT activity was significantly higher than the control under250mg·L-1stress.The contents of MDA were all higher than the control under three concentrations.Among them, MDA contents were significantly higher than the control under250mg·L-1and500mg·L-1stress. The effects of three kinds of antioxidant enzyme activities andMDA contents of I.sinensis under Pb and Cd stress are basically consistent. There wereno significant differences.2. Heavy metal Pb, Cd stress had influence on changes of I.sinensis DNAmethylation level and pattern. I.sinensis DNA methylation overall levels under threeconcentrations of Pb and Cd stress were basically consistent, respectively48.23%and48.10%. The control was46.96%. Compared with the control, I.sinensis DNAmethylation levels under Pb and Cd stress were increased slightly but not significantly.There was no significant correlation between the concentrations of Pb and Cd andI.sinensis DNA methylation levels. I.sinensis DNA methylation polymorphism underthree concentrations of Pb and Cd stress were respectively72.08%,76.50%,68.06%and94.48%,90.06%,89.81%. The addition of DNA methylation polymorphism ofI.sinensis under Cd stress and concentration of heavy metal was a negative correlation,while Pb had no significant correlation. The effect of changes of Cd on I.sinensis DNAmethylation polymorphism was greater than Pb. The overall methylation patternsshowed that Pb could induce DNA methylation degree methylation changes to more. Cdcould induce DNAmethylation degree demethylation changes to more. |
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