| The Cd and Pb are main metal pollutants in the environment, theyusually concomitantly exist in the nature. The Cd is not necessary for thepropagation, it is one of the most strong heavy metals of toxicity; The Pb isa kind of poisonous heavy metal element and can cause various physiologyabnormality. Most of Cd,Pb that got into the agriculture ecosystem systemexist on the soil surface, which bring harm to crop. We selected barley asthe material in our experiment, by indoor foster method and study the effectsof the Cd,Pb on Hordeum vulgare from the aspects of physiology andbio-chemistry, research results include the fllowing points:Firstly, effects of Cd,Pb and their combined pollution on thebiomass,the roots vigor and nitrate reductase activity (NRA) of barleyseedling were studied. The results showed that fresh and dried shoot weight,fresh and dried root weight of the barley seedling after 5d treated were lowerthan that of the control and declined with the increase of treatmentconcentrations. However, ratio of root to shoot (dried weight) of the barleyseedling after 5d treated was higher than that of the control and increasedwith the increase of treatment concentrations, that is to say, restraint function to shoot is stronger than root. Under the condition of Cd,Pb andtheir combined pollution roots vigor decreased drastically, roots vigor of 5dtreated was lower that of 3d treated. However, NRA increased in 5mg·L-1Cd,50mg·L-1 Pb and 5+50mg·L-1 (Cd+Pb). Afterwards, NRA declined asthe increase of treatment concentrations. By comparison, toxicity of Cd inbarley seedling was higher than that of Pb, toxicity of Cd+Pb combinedtreatment was higher than that of Cd,Pb single treatment.Secondly, effects of Cd,Pb and Cd+Pb in different concentrations on theelectric conductivity rate of leaf cells exosmosis liquor and the content ofproline and solube sugar in leaves of barley seedling after 3d and 5d treatedwere studied. The results indicated that with the increase of Cd,Pb and Cd+Pb concentrations, the content of proline and the opposite electricconductivity rate gradually increased; The content of soluble sugar increasedfirst and decreased afterwards. By comparison, toxicity of Cd in barleyseedling was higher than that of Pb, toxicity of Cd+Pb combined treatmentwas higher than that of Cd,Pb single treatment. Whether Cd,Pb singletreatment or their combined treatment, effects of Cd,Pb on barley seedlingafter 3d treated were always less than those after 5d treated.Thirdly, effects of Cd,Pb and their combined pollution onα-amylase,β-amylase and amylase isoenzymes in bourgeon seeds of the barley seedlingafter 5d treated were studied. The results showed that effects of Cd,Pb andtheir combined pollution onα-amylase,β-amylase are different, representing activation or inhibition,α-amylase activity enhanced in lowerconcentrations and declined in higher concentrations,β-amylase activityalways increased in all the treated concentrations. Adopting polyacrylamidegel electrophoresis(PAGE) method, amylase isoenzyme expressions werestudied. The results showed that amylase isoenzyme expressions basicallymade no difference in lower concentration, while were inhibited intensely inhigher concentration, for example, enzymatic strips became narrow,brightness became thin and a part of enzymatic strips disappeared. Bycomparison, toxicity of Cd in barley seeds was higher than that of Pb,toxicity of Cd+Pb combined treatment was higher than that of Cd,Pb singletreatment.Finally, adopting high performance liquid chromatography (HPLC)method, effects of Cd,Pb and Cd+Pb in different concentrations on thecontents of organic acid in barley root exudation was studied after the barleywas treated for 5 days. Four organic acids including citric acid, malic acid,lactic acid and oxalic acid in the exudates of barley root were detected. Theresults showed that with the increase of concentration, the contents of thefour organic acids were all higher than that of the control and increasedgradually. Moreover, the increased content of lactic acid in comparison withthe control is higher than the other three organic acids, the increased contentof oxalic acid in comparison with the control is lower than the other threeorganic acids. By comparison, toxicity of Pb in barley seedling in the treated concentrations was higher than that of Cd, toxicity of Cd+Pb combinedtreatment was higher than that of Cd,Pb single treatment.
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