| In the process of industrialization,some heavy metals enter into the soil by means of atmospheric deposition and sewage and cause pollution to the soil,which seriously threatens the ecological environment and people’s health.The remediation technology of heavy metal contaminated soil has become the focus of research in China and even in the world.Euphorbia pulcherrima(Euphorbia pulcherrima)is an important woody ornamental plant in the world.In this study,the cutting seedling of poinsettia sinensis was used as the experimental material,and the growth index of poinsettia growing in different volume ratios(0%,25%,50%,75%,100%)of heavy metal contaminated soil was determined by using incomplete random block design method.The contents of heavy metals in roots,stems,red bracts and green leaves of poinsettia were compared and analyzed,and the effects of heavy metals in contaminated soil on the growth and development of poinsettia and the remediation ability of poinsettia on contaminated soil were discussed.The purpose of this study was to investigate whether poinsettia has a remediation effect on heavy metal contaminated soil and to determine whether it is a heavy metal enrichment plant.The main research results are as follows:(1)Plant heights in 25%,50%,75%and 100%treatment groups were 93.57%,89.21%,70.17%and 42.17%of those in control group,respectively;The ground diameters of the control group were 85.96%,105.26%,112.28%and 84.21%,respectively.The number of green leaves increased with the increase of heavy metal content,and the fresh weight of leaves in 75%treatment group was significantly higher than that in control group.The leaf dry weight of 25%treatment group was the largest,and leaf area of 75%treatment group was the largest.The number of leaves,fresh weight and dry weight of red bracts in the high content heavy metal treatment group were significantly different,the quantity and quality of red bracts were decreased,and the leaf area in the 75%treatment group was significantly greater than that in the other treatment groups.The stem fresh weight decreased with the increase of heavy metal content.The stem fresh weight of the control group was 6.88g,and that of the 100%treatment group was 3.89g.The dry weight and fresh root weight of 25%treatment group were higher than those of control group,and decreased with the increase of pollution degree.The morphological characteristics of taproots in 25%treatment group were 51.03cm in length,87 taproots in tip number,and 18.14cm2 in surface area,which were all higher than those in control group,while the diameter of taproots was 1.23cm,and the volume of taproots was 0.54cm3,which were lower than those in control group.In 50%treatment group,the lateral root length was 238.02cm,the root diameter was 0.63cm,the number of root tips was 467,the lateral root surface area was 45.73cm2,and the volume was 0.7cm3,both of which were higher than those of the control group.(2)The content of chlorophyll a in 25%treatment group,50%treatment group and 75%treatment group had no significant difference with the control group,which was about 0.08mg/g.The content of chlorophyll a in 100%treatment group increased significantly,which was 0.13mg/g.The contents of chlorophyll b in the 25%treatment group,50%treatment group and 75%treatment group were 0.17mg/g,0.17mg/g and 0.15mg/g,respectively,which were all lower than the control group,and increased to 0.24mg/g in the 100%treatment group.The high pollution environment increased the content of chlorophyll.The content of anthocyanin increased with the increase of heavy metal content,and all the treatment groups were higher than the control group.(3)The contents of Cr,As and Cd in green leaf treatment group were all lower than those in control group.Cu content in 100%treatment group was 66.33%higher than that in control group,Hg content in 50%treatment group was 8.98%higher than that in control group,Zn content in 50%,75%and 100%treatment groups was all higher than that in control group,and Zn content in 100%treatment group was the highest.Higher than the control by 76.27%;Green leaves can enrich Cu,Hg and Zn.The content of AS in red bracts treated by 100%was 0.94%higher than that in the control.Cr was 0.096mg/g in 75%treatment group.The content of Cd in 25%treatment group was higher than that in control group by 115.59%.Cu content in 50%treatment group was higher than that in control group 292.66%;The Hg content of 75%treatment group was higher than that of control group(187.31%).Zn content in 75%and 100%treatment groups was 23.61%and 7.18%higher than that in control group,respectively.The bracts were enriched in Cd,Cu,Hg and Zn.The stem had no enrichment ability for Cu,but had strong enrichment ability for other heavy metals,which gradually increased with the increase of heavy metal content.The contents of Cr,As,Cd,Hg and Zn in 100%treatment group were 0.026mg/g,0.315μg/g,1.393μg/g,0.025μg/g and 0.094mg/g,respectively.The contents of Cu and Zn in taproots increased with the increase of heavy metals.Cu content and Zn content in 100%treatment group were 13 times and 18 times higher than those in control group,indicating strong enrichment.The contents of Cd,As and Hg were enriched only in 100%treatment group:the content of Cd was 11 times higher than that of control group,and the content of As and Hg were 24.51%and 96.51%higher than that of control group,respectively.Cr content was the highest in the control,which was 0.057mg/g,indicating that the taproot had no enrichment of Cr.The contents of Cd and Zn in lateral roots increased with the increase of heavy metal content,and the highest contents were 43.983μg/g and 1.387mg/g,respectively,which showed significant enrichment.In the 50%treatment group,the absorption of As was the highest,which was 16.55%higher than that of the control;in the 75%treatment group,the absorption of Cu was the highest,which was 9.45%higher than that of the control;the absorption of Cr and Hg was decreased first and then increased.The absorption of 100%treatment group was the highest,which was 60.08%and 30.32%higher than that of the control,respectively.(4)The metal enrichment capacity of each part is as follows:Cr:stem>lateral root>taproot>bract>green leaf;For heavy metal Cu:taproot>bract>green leaf>lateral root>stem;For Zn:taproot>stem>lateral root>green leaf>bracts;As:stem>bract>lateral root>taproot>green leaf;For heavy metal CD:Lateral root>stem>taproot>bract>green leaf;For heavy metal HG:Stem>bracts>taproots>lateral roots>green leaves.The transfer coefficient of CR in 75%treatment group was 1.73 higher than that in control group.The Cu transfer coefficient in 50%treatment group was 0.21 higher than that in control group.The transfer coefficients of Zn,Cd and As were the highest in the control group,indicating that the plant had a weak ability to transport Zn,Cd and As.The transfer coefficient of Hg in the 100%treatment group was lower than that in the control group,and that in the rest treatment groups was higher than that in the control group,and the most obvious value was 3.22 in the 75%treatment group,indicating that the plants had a strong transport capacity for heavy metal Hg. |
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