| With the rapid development of human society and economy,increasing in demand for mineral resources,the exploitation of mineral resources caused the damage of land and vegetation,causing environmental pollution,lossing of biodiversity,landslides,mudslides and geological disasters other a series of environmental problems.Thus,vegetation restoration of mining wasteland is very urgent.Since mining wasteland habitats very bad,poor plant growth,carrying out mining wasteland revegetation extremely difficult,become of urgent environmental science issue.Changting rare earth mine is typical ionic rare earth mine in southern China,the mining of rare earth has been caused the deterioration of the ecological environment of rare earth and around,urgently need to take measures to control.Our research Group of instructors conducted revegetation of rare earth mine which study found:Rare earth ore used acid extraction rare earth,leading to soil is too acid and heavy metal pollution,poor plant growth environment.But Neyraudia reynaudiana was able to grow normally in Changting rare earth mine wasteland,maintaining a high biomass.Neyraudia reynaudiana can grow in rare earth mine wastelands,which maybe have a special adaptation mechanisms of acid and heavy metal stress.But the researches on Neyraudia reynaudiana mainly in terms of soil erosion control,the root of the solid earth and its response to drought stress,etc.,and It is unclear that Neyraudia reynaudiana adaptation strategy on soil acid stress and heavy metal stress.In view of this,in the paper Neyraudia reynaudiana which can growing in Changting rare earth mine wastelands for the study,through indoor stress simulation test,designed to different levels of soil acidity and heavy metal stress condition,was measured at different stress conditions Neyraudia reynaudiana aerial part,root,chlorophyll,antioxidant enzymes,MDA,etc.morphology and physiology indexes,compared the differences of different stress of Neyraudia reynaudiana on acid and heavy metals in the morphological and physiological indicators,revealed Neyraudia reynaudiana the internal response mechanism on acid and heavy metal stress,provided a scientific basis for Changting rare earth mine wasteland vegetation restoration.The main findings are as follows:(1)Acid stress had less promotion effect on plant height,leaf width and leaf number growth of Neyraudia reynaudiana during early days,with the extension of the stress time,the promoting effect begame more obviously;but with the extension of the stress time,it gradually showed promotion;Acid stress treatments promoted rhizome length,root surface area,root volume and root mean diameter growth of Neyraudia reynaulidana.Under the treatment of pH4.5,rhizome length,root surface area,root volume and root mean diameter of Neyradia reynualidana reached the maximum.Acid stress treatments promoted biomass accumulation of Neyraudia reynaudiana Under the treatment of pH4.5,shoot,root and whole plant biomass of Neyraudia reynaudiana reached its maximum;under the treatment of pH5.0,growth of root biomass was larger than growth of the above-ground biomass which made root-shoot ratio reached a maximum;with acid stress intensity increased,all aboveground biomass,root biomass,the whole plant biomass of Neyraudia reynaudiana presented the tendency of increasing first and then decreasing.(2)Acid stress treatment promoted chlorophyll content of Neyraudia reynaudiana,in addition to pH3.5 were significantly higher than the control,which made chlorophyll a/b reach the maximum when treated by pH5.6.Acid stress treatments promoted Neyraudia reynaudiana's chlorophyll fluorescence parameters such as basic fluorescence F0,maximum fluorescence Fm,variable fluorescence Fv as well as photochemical efficiency of PSII Fv/Fm.With the pH stress intensity increased,maximum fluorescence Fm,variable fluorescence Fv as well as photochemical efficiency of PSII Fv/Fm of Neyraudia reynaudiana was presenting the tendency of increasing first and then decreasing,while the basic fluorescence FO the tendency of gradually decreasing;and pH5.0 treatment inhibited its potential PSII photochemical activity Fv/F0.(3)pH5.0 treatment promoted Neyraudia reynaudiana's leaves POD,SOD and CAT activities,instead,there was inhibition effect when treatment by other acid stresses,and with the acid stress intensity increasing,the inhibition became more obvious;Except for pH5.0 other acid treatment was significantly promoted Neyraudia reynaudiana's MDA content,and with the acid stress intensity increased,the promotion became more obvious.pH5.0 treatment promoted catalase,acid phosphatase and urease activity,other acids stress treatments inhibited them;under the same acids stress conditions,Neyraudia reynaudiana's rhizosphere soil enzyme activities were higher than non-rhizosphere soil enzyme activity.(4)Pb stress inhibited plant height,maximum leaf width during early days,with the extension of the stress time,it gradually showed promoting effect,but it took less promotion on Neyraudia reynaudiana's maximum leaf width;during the processing of Pb stress,Pb250 promoted the growth of the number of leaves,and other Pb stress treatment was no obviously difference;there was no significant effect on maximum leaf length and number of tillers during Pb processes.Pb treatments promoted them;under the treatment of Pb250,the average diameter of the Neyraudia reynaudiana's root was inhibited,but promoted by other treatment;with the increasing of Pb stress intensity,root length,root surface area and root volume of Neyraudia reynaudiana presented the tendency of increased first then decreased,however the average diameter of the root presented the tendency of decreased first then increased.Pb concentrations less than 750 mg·kg-1 treatment,the Neyraudia reynaudiana's aboveground biomass,root biomass and the whole plant biomass accumulation were promoted,but greater than 750 mg-kg-1 treatment is manifested as inhibition.(5)Pb stress treatment promoted chlorophyll a,chlorophyll b and chlorophyll a+b content of Neyraudia reynaudiana,reaching maximum under Pb250 treatment,and which significantly higher than other;Pb stress inhibited chlorophyll a/b content,and no significant difference between two different Pb stress treatments.Pb stress treatments promoted v's F0,Fm,Fv,furthermore,with the pH stress intensity increased,it presented tendency as increased first and decreased;Pb 500 treatment inhibited potential PSII photochemical activity Fv/F0;Pb stress treatments had no significant effect on the maximal photochemical efficiency of PSII Fv/Fm.(6)With increasing concentrations of Pb stress,POD,SOD and CAT activities in leaves showed a decreasing trend,and MDA showed a increasing trend.Pb250 promoted catalase activity in growing soil.Pb500 promoted urease activity in growing soil.Pb stress inhibited the soil acid phosphatase activity.Under the same conditions of Pb stress,the soil enzyme activities in roots were higher than that in non-roots.(7)With increasing concentration of Pb stress,Pb contents increases in root and aboveground of Neyraudia reynaudiana,the concentration of Pb in aboveground was all higher than that in roots.Under the Pb750 treatment,the maximum concentration of Pb in aboveground was 140 mg·kg-1,did not reach the content of abundant plants.(8)Each period Cd stress inhibited the growth of plant height,and with the increase of stress concentration showing a decreasing trend.Each period Cd stress,maximum leaf length and number of leaves were promoted growth in Cd-25,but other Cd treatment inhibited that.Early Cd stress inhibited Neyraudia reynaudiana maximum leaf width,along with the stress time,Cd had no significant effect on the growth of the largest leaf width.With increasing concentration of Cd stress,root length and root surface area of Neyraudia reynaudiana showed a decreasing trend,root volume of Neyraudia reynaudiana increased first,Cd stress promoted the growth of Neyraudia reynaudiana root mean diameter.With increasing concentration of Cd stress,aboveground biomass,root biomass and the whole plant biomass showed a decreasing trend.(9)Cd stress promoted chlorophyll a,chlorophyll b and chlorophyll a?b,and were significantly higher than the control;Cd stress inhibited chlorophyll a/b,and were significantly less than the other treatments.Cd stress promoted F0,Fm,Fv,Fv/Fm and PSII photochemical activity Fv/F0.With increasing concentration of Cd stress,chlorophyll fluorescence parameters increased first,but decreased then with the succession.(10)With increasing concentrations of Cd stress,POD,SOD,CAT activities in leaves showed a decreasing trend,and MDA showed a increasing trend.With increasing concentration of Cd,the activity of catalase,acid phosphatase and urease showed a decreasing trend in the soil.Under the same conditions of Cd stress,the soil enzyme activities in roots were higher than that in non-roots.(11)With increasing concentration of Cd stress,Cd contents increases in root and aboveground of Neyraudia reynaudiana,the concentration of Cd in aboveground was all higher than that in roots.Under the Cd 100 treatment,the maximum concentration of Cd in aboveground was 29.20 mg-kg-1,did not reach the content of abundant plants.It seemed that,In summary,Neyraudia reynaudiana mainly through root enlargement and root elongation,improved aboveground biomass and root tillering capacity,improved chlorophyll content,chlorophyll the based fluorescence,the maximum fluorescence,the variable fluorescence and PSII Potential photochemical activity,and so on ways to adaption to the soil acid stress;Neyraudia reynaudiana mainly through root elongation and formed stronger root network to avoiding Pb stress,improved chlorophyll content,chlorophyll the based fluorescence,the maximum fluorescence,the variable fluorescence and PSII Potential photochemical activity,increased Neyraudia reynaudiana aboveground biomass,transferred heavy metals in the soil portion to the aboveground,in order to weaken the heavy metals on root damage,thus Neyraudia reynaudiana can adapt to the environment of heavy metal stress. |
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