Effects of heavy metal stress on tobacco physiological characteristics and biomass.

In order to study the effects of four kinds of heavy metal stress on leaf protective enzyme action rules,apot experiment was conducted to study the effects of four kinds of heavy metal stress on physiological characteristics and biomass of flue-cured tobacco.Results:In vigorous growth period,the SOD activity reached the highest when Cd concentration was 0.5mg/kg,13.71%higher than the control; While 22.49%lower than the control when the concentration was 1.5mg/kg.Compared with the control, the CAT activity decreased gradually by 17.03% and 31.27% respectively.POD activity increased gradually by 11.73%and 19.43%respectively.MDA content increased gradually by 4.51% and 7.89% separately.When treated with Pb,the change trends of SOD,POD,CAT activities and MDA content were in accordance with Cd treatment.300 mg/kg Pb treatment made POD activity increased most significantly,21.63% higher than the control;With the increase of Hg concentration,SOD activity gradually increased,0.88% and 9.88% higher than the control respectively,CAT activity decreased by 11.76%and 32.51%respectively;MDA content increased by 3.38% and 11.65% separately.Under As stress,CAT activity decreased gradually by 21.05%and 36.53%separately.As had the greatest influence on photosynthetic rate,which decreased by 30.4% when As concentration was 40mg/kg.The biomass decreased under stress of heavy metals.