| With the development of the industrialization process,heavy metal pollution has become one of the major global environmental problems.Heavy metal pollution problems was also very serious in our country,along with the development of the western development strategy implementation,heavy metal pollutants in the road and industrial park of western region have showed continuous accumulation phenomenon,cadmium,lead,zinc content exceeded standard and affected the surrounding environment and human health.Fixed issues of heavy metal contaminated soil need attaches great importance urgently and practical solution in the western region.So it has important practical significance to select the appropriate phytoremediation species for environmental protection and pollution control in the western region.Four different kinds of cadmium treatment were applied to determine the growth,biomass,photosynthesis,autioxidant enzyme activities and cadmium concentration in various parts of Ulmus pumila ‘Jinye',Ligustrum obtusifolium,Tamarix ramosissima and Shepherdia argentea seedlings.The cadmium treatments were CK(0 mg·kg-1,control),T1(2 mg·kg-1),T2(5 mg·kg-1),T3(10 mg·kg-1).Through study tolerance ability,accumulation characteristics and growth,physiological and photosynthesis response of four Shurbs of Arid and Semi-arid Region to Cd that aim to ascertain four shurbs whether can be used in the vegetation restoration in surface soil cadmium pollution area in Ningxia and even whole western region in China;In order to investigation tolerance and accumulation characteristics and growth physiology,photosynthetic response of four Shurbs of Arid and Semi-arid Region to Pb,four different kinds of lead treatment were applied to determine the growth,biomass,autioxidant enzyme activities,photosynthesis and lead concentration in various parts of U.pumila ‘Jinye',L.obtusifolium,T.ramosissima and S.argentea seedlings.The lead treatments were CK(0 mg·kg-1,control),T1(400 mg·kg-1),T2(800 mg·kg-1),T3(1200 mg·kg-1);A pot experiment was conducted to evaluate the phytoremediation capability of U.pumila ‘Jinye',L.obtusifolium,T.ramosissima and S.argentea seedlings to zinc contamination.The saplings were exposed to different zinc concentration treatments,including CK(0 mg·kg-1),T1(300 mg·kg-1),T2(500 mg·kg-1),T3(1000 mg·kg-1),for 90 days in plastic buckets under the experimental greenhouse.Growth,biomass,photosynthesis and zinc content distribution in various parts of the plants were measured.The results of the experiments showed that:The plant height,biomass and tolerance index(Ti)of U.pumila ‘Jinye' had no significant difference compared with CK at 5.31 mg·kg-1 of soil cadmium content and plant height and biomass were suppressed when soil cadmium content raised to 10.31 mg·kg-1.The plant height,biomass and tolerance index(Ti)and Pn(net photosynthetic rate)of L.obtusifolium,T.ramosissima and S.argentea decreased with Cd content raised.Pn of U.pumila ‘Jinye' was not restricted when cadmium content was no more than 5.31 mg·kg-1.Peroxidase(POD)and catalase(CAT)of U.pumila ‘Jinye' were increased with Cd content raised and superoxide dismutase(SOD),ascorbate peroxidase(APX)activities raised at first,then decreased and the peak appeared at 5.31 mg·kg-1.Superoxide dismutase(SOD),peroxidase(POD),catalase(CAT)and ascorbate peroxidase(APX)activities of L.obtusifolium,T.ramosissima and S.argentea raised at first,then decreased and the peak appeared at 5.31 mg·kg-1.Cadmium contents in root of U.pumila ‘Jinye' reached the peak at 10.31 mg·kg-1,were 10.47 mg·kg-1 DW and translocation factor(TF)between 0.07-0.48.Cadmium contents in root of T.ramosissima achieved maximum was 5.03 mg·kg-1 DW and translocation factor(TF)between 0.85-3.57.Cd content in various parts of L.obtusifolium and S.argentea showed root> stem> leaf and translocation factor(TF)between 0.11-0.70 and 0.75-0.81 respectively.According to this study can be seen U.pumila ‘Jinye' had a high cadmium tolerance and root accumulation ability when cadmium content was no more than 5.31 mg·kg-1.T.ramosissima had a good Cd tolerance and most optimal transfer ability of cadmium to the ground.U.pumila ‘Jinye' and T.ramosissima had strong application potential in cadmium pollution area of Ningxia and even the whole western region in China.Although L.obtusifolium and S.argentea had a good Cd tolerance when Cd content was 5.31 mg·kg-1,its root accumulation ability and transfer ability of cadmium were worse compared with U.pumila ‘Jinye' and T.ramosissima,so potential applications ability was reduced.The plant height,biomass and Pn of U.pumila ‘Jinye',L.obtusifolium and T.ramosissima were reduced with Pb content raised when Pb stress after 90 days.The plant height,root biomass and shoot biomass of S.argentea had no significant change compared with CK.SOD,POD and APX activities of U.pumila ‘Jinye' achieved the maximum at Pb was 831.61 mg·kg-1 in soil and CAT activities achieved the maximum at Pb was 431.61 mg·kg-1,there was no significant difference of CAT activities between T1 and T2 treatment and were higher than that of CK.SOD,POD,CAT and APX activities of L.obtusifolium and S.argentea raised at first,then decreased and the peak appeared at 431.61 mg·kg-1.SOD,POD,CAT and APX activities of T.ramosissima continue to increased and the peak appeared at 1231.61 mg·kg-1.Pb content in various parts of four shurbs of arid and semi-arid region showed root> stem> leaf.TF of U.pumila ‘Jinye',L.obtusifoliu,S.argentea and T.ramosissima between 0.14-0.2,0.06-0.16,0.40-0.72,0.29-0.91 respectively.The results showed that U.pumila ‘Jinye' had a high Pb tolerance and root accumulation ability when Pb content was 831.61 mg·kg-1 and L.obtusifolium had a good Pb tolerance and active antioxidant capacity at Pb content was 431.61 mg·kg-1.Growth and photosynthesis of S.argentea were not received limit and showed the lead resistance ability and high transfer capability at Pb content was 431.61 mg·kg-1,that can be used in Pb pollution area of western region in China.While limited the growth and photosynthesis of T.ramosissima under Pb stress,activity of antioxidant enzymes continues to increased and with the best ability of transfer Pb to the ground part,and can be used to repair Pb-contaminated soil in western region of China.The plant height,root biomass,shoot biomass and chlorophyll content of U.pumila ‘Jinye',L.obtusifolium,T.ramosissima and S.argentea were reduced with Zinc content raised.The root-shoot rate of U.pumila ‘Jinye' had no significant change compared with CK when soil zinc content was 425 and 625 mg·kg-1 respectively and reduced significantly at 1125 mg·kg-1 of soil zinc content.The root-shoot rate of L.obtusifolium and S.argentea were reduced at 625 and 425 mg·kg-1 of soil zinc content respectively.On the contrary,the root-shoot rate of T.ramosissima continuously raised with zinc content increased.The Pn,stomatal conductance(Gs),intercellular CO2 concentration(Ci)of four shurbs of arid and semi-arid region were reduced with zinc content increased,it suggested that stomatal closure was the reason why Pn decreased.Zinc contents of root,stem and leaf of four shurbs of arid and semi-arid region were higher than CK and reached the peak at 1125 mg·kg-1.Zinc content in various parts of four shurbs showed root> stem> leaf.The TF of U.pumila ‘Jinye',L.obtusifolium,T.ramosissima and S.argentea between 0.84-1.20,0.63-0.70,0.82-1.31,0.62-1.39.The conclusion was that growth of L.obtusifolium was limited by high concentrations of zinc and leaf senescence increased,meanwhile its low transfer coefficient made ability to repair soil zinc pollution reduced.U.pumila ‘Jinye',T.ramosissima and S.argentea had good resistant ability and transfer ability of zinc when soil zinc content was no more than 625 mg·kg-1,therefor can be used in zinc pollution area of western in China. |
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