The Effect of Pb-Cd Composite Stress on Seedling Growth of the Three Kinds of Asteraceae

In order to prove the patience of Cosmos bipinnatus,Zinniaelegans and Centaurea cyanus Linn.the effect of different concerntration of Pb-Cd composite stress on seed germination and growth of the three kinds of Asteraceae was studied.The results showed that the germination rate,fresh weight and plant height of Cosmos bipinnatus,Zinniaelegans and Centaurea cyanus Linn were increased with the concentration of Pb-Cd increased under the low concentration of Pb-Cd composite stress,but all the indexes decreased when the Pb-Cd concentrationmore than 750-40 mg·L-1;The value of root cap rate of Zinniaelegans and Centaurea cyanus Linn increased with treatment concentration of Pb-Cd increased,but the value of root cap rate decreased significantly when the Pb-Cd concentrationmore than 750-40 mg·L-1,the value of root cap rate of Cosmos bipinnatus steadily reduced with the Pb-Cd concentration increased;The value of root cap rate,fresh weight and plant height of three kinds of composite were Centaurea cyanus Linn Zinniaelegans Cosmos bipinnatus.