Study On Antioxidant Enzyme Activity And Photosynthetic Characteristics Of Cd-Hyperaccumulator Galinsoga Parviflora

In this peper,Galinsoga parviflora was used to study the ability of enrichment to cadmium,and antioxidant enzyme expression feature and activity and photo-physiological characteristics, with different concentration of cadmium (soil Cd concentration were 0,25,50,75,100 mg·kg-1).The main results were as follows:(1)Study on enrichment capability:Over 75 mg·kg-1 Cd treatments, the concent of overground part were 102.16 mg·kg-1 and 137.63 mg·kg-1, the Bioconcentration coefficients and the Translocation coefficients were exceeded 1.0,all of these values exceed the critical value of Cd-hyperaccumulator. In all treatments,the Absorption volume coefficients were 4.30-8.22,the Transfer volume coefficients were 6.23-6.91,the accumulation in shoots and roots were 107.46μg·plant-1～205.62μg·plant-1、17.45μg·plant-1～31.50μg·plant-1.So,it was a Cd-hyperaccumulator.(2) Study on antioxidant enzyme activity:When the Cd concentrations in soil were less than 75 mg·kg-1, the activities of SOD and POD were increased,when the Cd concentrations more than 75 mg·kg-1, the activities of SOD and POD were decreased. All concentrations of Cd inhibited the activities of CAT,the activities of CAT in other treaments all lower than the control.(3) Study on isozyme expression:The isozyme expression of POD and CAT in G. parviflora leaves were promoted under Cd stressed. When the Cd concentrations in soil were 50 mg·kg-1 to 100mg·kg-1,it induced the expression of POD-1 and POD-2, when the Cd concentrations in soil were 75 mg·kg-1 and 100mg·kg-1,it induced expression of CAT-1 and CAT-2,and the expression quantity increased with the increase of the concentration of Cd.(4) Study on antioxidant photosynthetic physiology:Under the stress of different Cd concentrtion,the content of chlorophyll a, chlorophyll b,carotenoids and the total chlorophyll of leaves were decreased.The decreased in net photosynthetic rate was restricted by non-stomatal factors, as the Photosynthetic rate(Pn), Stomatal conductance(Gs),Transpiration rate(Tr), Intercellular CO2 concentration(Ci) were decreased with Cd increased,but Limiting value of stomata(Ls) were increased. At the same time, G. parviflora remitted the poisoning symptoms by increasing water use efficience and stomatal limitation.(5) Study on chilrophyll fluorescence parameters:The Photochemical quantum yield (ΦPS Ⅱ), Photosynthetic electron transfer rate (ETR), Photochemical quenching (qp) of leaves were decreased with Cd increased,and the Non-Photochemical quenching (NPQ) was opposited.The stress of Cd limited the function of Photosynthetic system,decreased the quantum yield, decreased the amounts of nitrogen fixation and oxygen release. The G. parviflora by dissipating the heat to remitted the damage of Cd stress.In conclusion,G. parviflora were grew well under all treatments.When the content of Cd in soil were more than 75 mg·kg-1，the content of Cd in shoots, bioconcentration coefficients in shoots and the translocation coefficients in shoots were reached the standard of Cd-hyperaccumulator.So,it was identified as a new Cd-hyperaccumulator of weeds. It was important for reparing polluted farmland by Cd,and it could be a substantial material basis for farmland repairing system.