Study On The Effect Of Single And Combined Heavy Metal(Cu,Cd,Hg)on The Growth And Development Of Wheat

The effect of single and combined heavy metal (Cu,Cd,Hg) on the growth and development of wheat(Triticum aestivum L., CV: Yangma NO. 10) were studied. The emphasis of the research was placed on the major molecular mechanisms of Cu,Cd,Hg and combined pollutions damage to wheat. The results showed as follows:1. Effect of single and combined heavy metal pollutions on the growth and development morphology of wheatThe seed germinating was inhibited by the heavy metals. The seed germinating percentages treated by combined pollutions(Cu-Hg,Cd-Hg,Cu-Cd-Hg), except Cu-Cd combined pollution, were lower than the average percentage treated by single pollution(Cu,Cd,Hg). This illuminated that there was amplification effect of combined pollutions inhibiting seed germinating. Cu,Cd,Hg and their combined pollutions affected wheat growth and development. They not only inhibited the growth rate of wheat seedling, but also caused the leaves to become withered and yellow. The grains per ear treated by combined pollutions, except Cu-Cd pollution, were lower than that treated by single pollution, on the contrary , the 1000-gram weight treated by combined pollutions were higher that treated by single pollution.2. Effect of single and combined heavy metal pollutions on metabolism in wheat 2.1. Effect of single and combined heavy metal pollutions on respirationThe low concentration of Cu,Cd,Hg enhanced the leaf respiratory rate. However, the high concentration of Cu,Cd,Hg inhibited the leaf respiration. All concentration of Cu,Cd,Hg inhibited root respiration significantly. The combined pollutions inhibited a -amylase activity obviously, but induced B -amylase activity to be higher than that treated by singled pollution. Cu,Cd,Hg inhibited MDH activity in leaf and root, but low concentration of Cu,Cd,Hg enhanced MDH activity and isozymes expression in ear. The COD activity in leaf was inhibited by Cu,Cd,Hg, but the COD isozymes expression in ear was stimulated.2.2 Effect of single and combined heavy metal pollution on the nitrogen metabolism in wheatCu,Cd,Hg inhibited the analysis of protein in germinating seeds, and inhibited the synthesis of protein in leaf of wheat.3. Single and combine heavy metal pollutions caused membrane lipid-preoxidation and the antioxidant enzyme respondence to peroxidationstressThe single heavy metals (Cu,Cd and Hg ) could induce the membrane lipid-peroxidation and increased the MDA content in leaf. The combined pollution caused the MDA content in leaf to be much higher. The results indicated that, the combined pollutions had amplification effect on inducing lipid-peroxidation.The low concentration of Cu,Cd,Hg induced the expression of SOD isozymes in leaf and ear, but high concentration of Cu,Cd.Hg inhibited the expression of SOD isozymes in root. The high concentration of Cu inhibited the expression of POD isozymes in leaf, but low concentration of Cd,Hg induced POD isozymes in leaf obviously. 0.1mmol/L Cu,Cd,Hg induced CAT activity, but 1.2mmol/Kg inhibited CAT activity.The SOD and POD activity in wheat treaded by 1.2mmol/Kg combined pollution of Cu,Cd,Hg was higher than that treaded by singled pollution, but the CAT activity was inhibited by 1.2mmol/Kg combined pollution of Cu,Cd,Hg. This result indicated that the combined pollution of Cu,Cd,Hg inducing peroxidation in wheat was related to the inhibition of CAT activity.4. Heavy metal stress induce DNA damage in wheatThe low concentration of Cu,Cd,Hg induced DNA content in wheat to increase, and caused DNA to break. Different concentration of Cu and low concentration of Cd and Hg induced DNA-protein cross-linking. The high concentration of Cd and different concerntration of Hg might induce DNA interstrand cross-linking.