Response Of Two Species Of Rorippa To Different Cadmium Concentrations And Water Conditions

Cadmium（Cd）is the main element that causes heavy metal pollution in soil.The treatment and restoration of soil contaminated by Cd has become a practical problem that needs to be solved urgently.Rorippa sylvestris and Rorippa amphibia are perennial herbs of the genus Rorippa in Cruciferae,Its not only have strong root and tiller reproduction ability,but also have resistance to pruning,fast growth,trampling,strong resistance,extensive management and low economic cost.Its can be used as an ideal garden ground cover plant for Cd contaminated soil remediation.The effects on growth of 2 species of Rorippa were studied under conditions of different concentrations of Cd(0,1,5,10,50,100,200,mg·kg^-1)and the different moistures（relative soil water content of 30～40%,50～60%,70～80%,90～100%,3～5cm flooding）soil detained by Cd of 50mg·kg^-1through pot experiment and artificial water control methods,and the change rules of photosynthetic characteristics,cadmium enrichment and transport capacity,and the effects of Cd on other 8 mineral nutrient elements were analized.This research will provide theoretical direction for two species of Rorippa applied to the ecological restoration of Cd-contaminated soil.The results were as follows:（1）Under different concentrations of Cd stress,two species of Rorippa could maintain normal growth,and their physiological indicators showed a trend of first rising and then falling with the increase of Cd concentration,showing‘low promotion and high inhibition’.Two species of Rorippa had strong abilities of Cd enrichment and translocation,the BCF of shoot,BCF and TF of plant were more than 1.When the Cd concentration was below 100 mg·kg^-1,the translocation ability Rorippa sylvestris was stronger than that of Rorippa amphibia.The relation between the absorption of Cd and the absorption of Ca,Mg,Zn were antagonistic,or the relation between the absorption of Cd and the absorption of Cu,Fe,P,Mn were synergistic.（2）In Cd contaminated soil,two species of Rorippa had strong resistance to drought and flood,and its were strong after processing 70 d,the drought-resistant ability of Rorippa amphibia was stronger than that of Rorippa sylvestris.Under different soil RWC conditions,shoot BCF,plant BCF and TF of Rorippa sylvestris were more than 1,and the Cd content of shoot dry weight per kg was greater than 100 mg,the translocation ability was poor under flooding conditions,and a large amount of Cd concentrated in the roots.Except for flooding,both shoot BCFand TF of Rorippa amphibia were more than 1,and the Cd content of shoot dry weigh per kg was more than 100 mg.The accumulation ability of Rorippa sylvestris was stronger than that of Rorippa amphibia;When the soil relative water content was 70～100%,plant growed well and the amount of the absorption and accumulation of cadmium in plant reached the biggest.