Different Concentrations HgCl₂ On Physiological And Biochemical Characteristics Of Three Kinds Macrophytes

13 kinds of aquatic plants,widely planted in Suzhou have been collected for this experiment.3 kinds aquatic plants,Sagittaria sagittifolia L.,Canna generalis Bailey and Iris pseudacorus L.,have been screened for further studies according to their biomass changes in Hoagland nutrient solutions with different Hg²⁺concentrations.The effects of different Hg²⁺concentrations on biochemical and physiological characteristics of these three kinds plants have been investigated on the basis of that the influences of different Hg²⁺concentrations on the biomasses,root architectures,photosynthetic parameters,physiological and biochemical properties and comprehensive evaluation with hydroponics.The results obtained are listed as follows:?1?The sequence have been found:emergent aquatic plant>floating plant>floating-leaved plant>submerged plant,according to screening experiments,within different concentrations of Hg²⁺,Sagittaria sagittifolia L.,Canna generalis Bailey and Iris pseudacorus L.have the highest biomass increment.So these three aquatic plants have used for the further studies.?2?With the increasing of Hg²⁺concentrations in nutrient solutions,Chl,Pn,Gs,Ci and Tr of Sagittaria sagittifolia L.increased,the highest values of Chl and Pn were observed at 1.0 mg·L^-1 Hg²⁺in nutrient solutions,whlie the highest values of Gs?Ci and Tr were observed at 2.5 mg·L^-1 Hg²⁺in nutrient solutions.However,with the further increasing of Hg²⁺concentrations in nutrient solutions,these characters continued to decrease.With the increasing of Hg²⁺concentrations in nutrient solutions,Chl,Pn,Gs,Ci and Tr ofCanna generalis Bailey and Iris pseudacorus L.decreased inversely.?3?With the increasing of Hg²⁺concentrations in nutrient solutions,total roots lengths of Sagittaria sagittifolia L.and Canna generalis Bailey increased,the highest values were observed at 2.5 mg·L^-1 Hg²⁺in nutrient solutions,with the further increasing of Hg²⁺concentrations in nutrient solutions,total lengths of roots continued to decrease.However,with the increasing of Hg²⁺concentrations in nutrient solutions,total roots lengths of Iris pseudacorus L.decreased.The total surface ares and volumes roots of Sagittaria sagittifolia L.presented a increasing first and then decreasing tendency with the increasing of Hg²⁺concentrations,and the highest value at 2.5 mg·L^-1 Hg²⁺,however,with the increasing of Hg²⁺concentrations in nutrient solutions,the total surface areas and volumes roots of Canna generalis Bailey and Iris pseudacorus L.decreased.Compared with the control,1.0 mg·L^-1 to 20.0 mg·L^-1 Hg²⁺concentrations did not contribute significantly to tips of roots of Sagittaria sagittifolia L.,nevertheless,when concentrations of Hg²⁺reached 40 mg·L^-1,Compared with the control,the tips of SagittariasagittifoliaL.reducesignificantly.Withtheincreasingof HgCl₂concentrations in nutrient solutions,the roots tips of Canna generalis Bailey and Iris pseudacorus L.decreased,But Compared with the control,it had no significant effect on Canna generalis Baileys',when concentrations of Hg²⁺reached 5.0 mg·L^-1,Compared with the control,the roots tips of Iris pseudacorus L.reduce significantly.?4?With the increasing of Hg²⁺concentrations in nutrient solutions,MDA content,Pro content and POD activities of three kinds macrophytes continued to rise,SP content and CAT activities increased and then decreased.SOD activities of Canna generalis Bailey and Iris pseudacorus L.continued to rise with the increasing of Hg²⁺concentrations in nutrient solutions,SOD activities of Sagittaria sagittifolia L.presented a increasing first and then decreasing tendency with the increasing of HgCl₂stress.?5?After the analysis through the membership function method,the results show that the mercury tolerance of Canna generalis Bailey and Sagittaria sagittifolia L.is close,while Iris pseudacorus L.has lower tolerance Compared with Canna generalis Bailey and Sagittaria sagittifolia L..