Study On The Tolerance Of Landscape Plants And Stabilization Under Heavy Metal Stress

In order to clarify the tolerance of landscape plants to heavy metals,ensure the normal growth of landscape plants in heavy metal contaminated soil,and realize the ecological landscape restoration of garden plants in heavy metal contaminated soil.This paper takes landscape plants as research objects and uses hydroponics and soil culture methods to clarify the physiological responses tolerance mechanism of landscape plants to heavy metals,systematically expounding the stable repairing effect of landscape plant combined stabilizer on heavy metals in soils.The research results mainly include:(1)The physiological responses and tolerance characteristics of Pb,Zn,Cu,and Cd in landscape plants(Rhododendron radendum,Gardenia jasminoides Ellis,Euonymus alatus Sieb.and Photinia serrulata Lindl.)were studied by hydroponic experiments.The results indicated that the SPAD values in leaves of Rhododendron radendum,Euonymus alatus Sieb.and Photinia serrulata Lindl.showed significant reduction due to treatments of heavy metals compared with control.Maximum reduction in SPAD values was observed in plants of Rhododendron radendum and Photinia serrulata Lindl..The content of MDA in plant leaves increased,and the treatment of Cd had a significant effect on the MDA content of leaves of Photinia serrulata Lindl.,which increased by 78.3 % compared with the control.The MDA content of Rhododendron and Euonymus leaves was not significantly different from the control.The content of proline in leaves of Euonymus alatus Sieb.was severely affected in Pb contaminated treatment,which was increased by 79.2 %.The enrichment coefficients of heavy metals in all four kinds of plants were more than 1,especially in roots and stems.Rhododendron simsii Fang exhibited high translocation of Pb and Cd.The Photinia serrulata Lindl.and Euonymus alatus Sieb.have respectively showed high translocation of Zn and Cu.The four kinds of landscape plants are not hyPeraccumulators,but they have certain repairing ability to lead-zinc-contaminated soil,especially Rhododendron radendum and Gardenia jasminoides Ellis.They have strong absorption and enrichment ability for Pb and Zn,and can be used as a potential tree for repairing lead and zinc contaminated soil.The effect of the absorption and accumulation of Euonymus alatus Sieb.and Photinia serrulata Lindl.is slightly weaker,but showed some tolerance to the four heavy metals.(2)The pot experiment was carried out to study the effects of superphosphate,zeolite and their combination on the physiological changes of two landscape plants(Gardenia jasminoides Ellis,Rhododendron radendum)in the heavy metal-polluted soils and the contents of heavy metals in shoots and roots.The soil pH,soil nutrients and heavy metal extracted content were analyzed with the application of amendments.The results showed that the treatment of the amendments increased the biomass of the plant shoots,increased the chlorophyll content of the plant leaves,and significantly reduced the uptake of heavy metals in plants,promoting the growth of the plants.DTPA-extractable Pb,Zn,Cu,and Cd concentrations were signicantly(p<0.05)decreased in the Gardenia jasminoides Ellis,Rhododendron radendum planted soils.The application of superphosphate reduced the content of DTPA-Pb in soil,the most significant reduce can be seen in G.jasminoides Ellis planted soil,which was 43.23 % lower than that of the control,thereby significantly reducing the uptake of Pb by 53.5 % in shoot of plants.The application of zeolite significantly reduced the content of DTPA-Zn,Cu and Cd in soil.The extractive content of all heavy metals(Pb,Zn,Cu,Cd)decreased significantly in the mix amendments treatments.Pearson correlation analysis indicated the higher correlation coefficient between G.jasminoides uptake metals and DTPA-extractable metal contents in soils from that of the R.radendum.Therefore,mixed application of amendments combined with G.jasminoides Ellis can effectively immobilize heavy metals,maintain the normal growth of plants in heavy metal contaminated soil environment,and realize the ecological restoration function of landscape plants on the soil in the mining area.Through the analysis of the physiological response and accumulation of heavy metals in landscape plants,it was found that it showed certain tolerance to heavy metals.It is feasible to add stabilizers combined with landscape plants in heavy metal contaminated soil in mining areas.Different plants have different tolerance mechanisms for heavy metals,and different stabilizers have different stabilizing effects on heavy metals.Therefore,it is necessary to find and screen more potential tree species,develop more valuable modifier materials,and digging deeply into the tolerance potential of landscape plants for heavy metals from molecular and genetic levels,which can provide technical support for realizing the greening of the mining area and improving the ecological landscape of the mining area.