Effects Of Cd?Pb?Cu?Zn On The Growth Of 3 Aquatic Leaf Vegetables And Mitigation Of Heavy Metals Pollution By Se Treatment

Watercress?Nasturtium officinale R.Br.?,water dropwort?Oenanthe stolonifera D.C.?and water spinach?Ipamoea aquatic Forstk?are 3 common aquatic leafy vegetables with more tender stems and leaves for food,which are nutrient-rich,with more high economic and social benefits.In this paper,a hydroponic experiment was carried out to study effects of Cd,Pb,Cu,Zn near the concentration prescribed by Environmental Quality Standards for Soils,on physiological characteristics,heavy metal accumulation and production.As well,the effect of Se on physiological characteristics,heavy metal accumulation,Se accumulation and yield of watercress,water dropwort and water spinach under Cd,Pb,Cu,Zn stress were studied,in order to provide some scientific evidences for the safety production of watercress,water dropwort and water spinach.The results were as follows;1.Cd concentration of watercress,water spinach and water dropwort may exceeded the limit prescribed by GB2762-2012,when Cd concentration in environment under the limit prescribed by GB15618-2008;Pb concentration of the 3 kind of aquatic leaf vegetables may under the limit prescribed by GB2762-2012,even when Pb concentration in environment exceeded the limit prescribed by GB 15618-2008.Cd concentration and Pb concentration of ediable part of watercress exceeded the national sdundard limited value,when Cd concentration and Pb concentration was 0.20 mg�L^-1 and 200 mg�L^-1 in nutrient solution.Cd concentration and Pb concentration of ediable part of DaYe and LiuYe water spinach exceeded the national sdundard limited value,when Cd concentration and Pb concentration was 0.40 mg�L^-1 and 150.00 mg�L^-1 in nutrient solution.Cd concentration and Pb concentration of ediable part of D07 and G0601 water dropwort exceeded the national sdundard limited value,when Cd concentration and Pb concentration was 0.40 mg-L^-1 and 200.00 mg-L^-1 in nutrient solution.Watercress was most easily polluted by Cd,water spinach secondly,and water dropwort has lowest on Cd accumulation.Water spinach growing was especially vulnerable to the Pb pollution,watercress after it,and water dropwort was lowest on the accumulation of Pb.There are also differences in accumulation ability to heavy metals in different varieties and strains of water spinach and water dropwort.With the increase of Cd,Pb,Cu,Zn concentration,the content of these heavy metals in different parts of watercress,water dropwort and water spinach will rise as well.The heavy metal content in different parts showed that root>leaf>stem.The abundant accumulation of heavy metal in roots is also one of the mechanisms of plant resistance to heavy metal stress.The content of Cu and Zn in 3 kinds of aquatic leafy vegetables have not exceeded the standard in this experiment,but the yield of watercress was the most vulnerable to the influence of Cu,Zn,water spinach was second,and water dropwort has the highest tolerance on Cu,Zn.2.Low concentration of Cd,Pb,Cu,Zn treatment,can improve root acitivity,soluble sugar content and photosynthetic efficiency of watercress,water dropwort and water spinach,but with the increase of concentration of Cd,Pb,Cu,Zn,these physiological indexes were depressed.The content of MDA and proline kept a persist increase belong to the rising on treatment concentration of Cd,Pb,Cu,Zn.Different physiological indexes had different sensitivities to heavy metals,the content of MDA and proline were vulnerable to the influence of Cd,Pb,Cu,Zn.Watercress is most sensitive to Cd,Pb,Cu,Zn in the three kinds of aquatic leafy vegetables.Lower concentrations of Cd,Pb,Cu,Zn stress will result in a significant increase of MDA content in watercress leaves.Therefore,we should pay more attention to the problem of heavy metal stress in watercress production.Different varieties or strains have different heavy metal tolerance in the same vegetable species.DaYe is more susceptible to heavy metals than LiuYe in two water spinach varieties while D07 is more susceptible than G0601 in two water dropwort varieties.3.Different antioxidant enzymes have different tolerances to heavy metal as well as antioxidant enzyme activities between different kinds of vegetables and different species or strains.SOD,POD,SOD,proline and PCs have a synergistic effect in alleviating the poisoning of the heavy metal.Antioxidant enzyme activities and PCs levels of the three kinds of aquatic leafy vegetables continued to rise under low concentrations of Cd,both had a synergistic effect under low concentrations of Cd.Antioxidant enzyme activities of the three kinds of aquatic leafy vegetables increased first and then reduced,while the content of PCs kept increasing with the concentrations rising of Pb,Cu,Zn.Antioxidant enzymes and PCs in the three kinds of aquatic leafy vegetables have a synergistic effect in alleviating the stress of the heavy metal under low concentrations of Pb,Cu,Zn.However,activities of antioxidant enzyme in three aquatic leafy vegetables were restrained and proline and PCs play an important role in alleviating the stress of high level heavy metal.4.Suitable concentration of Se treatment can reduce heavy metal content and improve Se content and the yield of three kinds of aquatic vegetables under the stress of Cd,Pb,Cu and Zn.But the yield would decresed at high level Se treatment.The suitable Se concentration varied with the different vegetables and different heavy metals.The most suitable Se concentration in alleviating Cd and Pb stress of watercress were 3.00 mg�L^-1?5.00 mg�L^-1;the most suitable Se concentration in alleviating Cu and Zn stress of water spinach were 3.00 mg-L^-1.The most suitable Se concentration in alleviating Cd,Cu and Zn stress of watercress were 10.00 mg�L^-1.The most suitable Se concentration in alleviating Cd,Pb,Cu and Zn stress of water dropwort were 5.00 mg-L"15.Under the condition of Cd?Pb?Cu?Zn stress,appropriate concentration of Se can enhance the antioxidant capacity of the 3 kinds of aquatic leaf vegetables,by improving root activity,antioxidant enzymes SOD,POD and CAT activity,proline and PCs content and photosynthetic efficiency,reducing MDA content in three kinds of aquatic leafy vegetables,to improve the growth of the 3 kinds of aquatic leaf vegetables.However,an excessive dose of Se,can increase toxicity of Cd?Pb?Cu?Zn.