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Developing bioenergy plants in heavy metal polluted soil can not only solve the problem of occupy arable land by energy plants replace with staple food crops,but also be able to obtain more economic and ecosystem benefits.As one of important bioenergy grasses,switch grass(Panicum virgatum L.)was used for this experiment.Two ecotypes of switchgrass,Alamo(lowland type)and Cave-in-rock(upland type),were used to examine the morph-physiological responses to cadmium(Cd)stress treated with 10,20 and 40μmol/L CdCl2 in a hydroponic experiment.The main results showed that both Alamo and Cave-in-rock can still survive even in 40 μmol/L CdCl2 condition.The plant biomass,water content,chlorophyll content,total root length,root surface area,root volume,number of root tips and root forks of two tested switch grasses were significantly decreased when exposed to Cd treatment.However,the ratio of root/shoot,average diameter of root and cadmium accumulation in plants were significantly increased after Cd Stress.Cave-in-rock accumulated higher Cd than Alamo in root,and its root length,root surface area and root volume of the former were dramatically higher in the 0.3-0.9 mm root diameter classes than those of Alamo,which mean a well-developed root system may contribute to higher Cd accumulation in Cave-in-rock.There were no significant difference(P>0.05)in Cd-tolerance between Alamo and Cave-in-rock at seedling stage.The translocation factors of Alamo were notably higher than those of Cave-in-rock,but uptake and accumulation ability of Cd in Cave-in-rock obviously exceeded the capability of Alamo.On the whole,both Alamo and Cave-in-rock are suited to be developed as bioenergy plants and/or bioremediation plants in Cd contaminated soil.