Studies On Resistance Of Aralia Elata Var.inermis To Heavy Metal In Soil

Aralia elata var.inermis,commonly known as fewer thorns Aralia mandshrica,has the high nutritional and medical value,which the young leaves are ediblea and rich in nutrient and bioactive components such total saponins,dietary fiber, flavonoid etc.The heavy metal:Pb,Cd,Hg etc, of soil in Tianjin,typical sewage irrigated area,was above the national standards,threatened the quality and safety of vegetables. Aralia elata var inermis is woody vegetable,Roots and Stems developed,accumulated more heavy metals in root,less in leaf.The root activity and rhizosphereplant microorganisms of plants were restrained under heavy metal stress in soil, thus physiological indexes of plants such as leaf growth were inhibited,the production and safety of woody vegetables were affected.It was studied the impact of lead,cadmium,mercury on the Growth status,quality,Antioxidant systems of Aralia elata var inermis in condition of pot experiments.At the same time the absorption and migration of heavy metal in Aralia elata var.inermis,the tests showed that:(1) The poison function of Arlia elata var inermis was not significant under the stress of three heavy metal, the leaf morphology and leaf color were normal.Bud length, crown-width and tiller number were different but not obvious. Germination period of Arlia elata var.inermis put off,but not obvious.With the increase of metal addition, the fresh weigh water content of Aralia elata var.inermis increased to the maximum and then decreased. The changing tendency of relative water and water saturation deficit of the leaf is contrary but not obvious.(2) When treated with Pb, Cd, Hg, the quality indexs were affected in some degree, such as protein, organic acid, soluble sugar and so on. The content of soluble protein increased firstly and then decreased with the increase of the concentration of Pb,and decreased with the increase of the concentration of Cd and Hg. The synthesis of soluble protein was inhibited under the stress of Hg. When treated in low concentration of Pb and Cd, the formations of malic acid and tartaric acid were promoted. The effects of low concentration of Hg on malic acid and tartaric acid were not significant. Low concentration of Pb and Cd promoted the synthesis of soluble sugar, while the high concentration inhibited the synthesis. There was inhibition in the synthesis of soluble sugar on the whole. The content of soluble sugar reached the minimum of12.44mg/kg when treated in the concentration of10mg/kg of Hg. The heavy metal of Pb, Cd, Hg inhibited the synthesis of Vc in some extent,When treatment with cadmium20mg/kg,the content of vitamin C reached a minimum of98.60mg/kg.(3) The effect of heavy metals (Pb,Cd,Hg) on antioxidant system (MDA,POD,CAT and hlorophyll)of Aralia elata var.inermis was that with the increase of Pb,Cd,Hg addition the changing tendency of antioxidant system increased to the maximum and then decreased,in total.The changing tendency of the MDA,POD,CAT,chlorophylla and chlorophyll a+b increased to the maximum and then decreased under Pb stress. The changing tendency of,POD,CAT,chlorophyll a and chlorophyll a+b increased to the maximum and then decreased under Cd stress,while MDA always raised and to be maximized at20mg/kg.The changing tendency of,POD,CAT increased to the maximum and then decreased under Hg stress,while MDA,chlorophyll a and chlorophyll a+b always raised.The metal lead,cadmium and mercury could inhibit the synthesis of chlorophyll b.(4) It was different that heavy metal accumulation effect of Aralia elata var.inermis on different organization and date.With the increase of metal addition and the extending of time,the lead, cadmium and mercury content of leaf were increased of a certain degree. The content of lead in the root was the higher than that in stem bark and Capillary root. It shows that Capillary root was difficult to accumulate lead. The content of cadmium in the root was higher than in capillary root and stem bark. It shows that cadmium could be accumulated in root, stem bark and capillary root. When treated in Pb(0～300mg/kg), Cd(0～2mgkg), Hg(0～0.5mgkg), the contents of Pb, Cd, Hg in leaves of Arlia elata var.inermis were lower than the maximum residue limits of contaminants in food of China--leaf vegetables(GB2162-2005), it is safe for us to eat. The higher of the concentration and the longer of the stress time it is, the greater of the toxicity in eating will become.(5) It was different that the absorption of Aralia elata vaninermis mineral elements under different heavy metal and different concentration stress.The uptake of Cu decreased in the leaf of Aralia elata var.inemis treated with Pb,Cd and Hg.With the increase of metal addition, the Fe,Mg. Zn content of Aralia elata var.inermis in leaf (15d)increased to the maximum and then decreased. At the same time,The uptake of Fe,Mn,Zn increased in the leaf (30d)of Aralia elata var.mermis,but not provious On Mg. The Cu,Zn content of Aralia elata var.inermis in leaf (15d) was higher than in leaf (30d),but The Fe,Mg content of Aralia elata var.inermis in leaf (30d) was higher than in leaf (15d)。We could see that Fe,Mn were easier accumulated in the leaf.