Response And Accumulation Of 3 Sedums To Cadmium And Lead Stress

With the accelerated development of industrialization and urbanization,the soil environment has become more and more serious.The soil heavy metal pollution,one of the most serious threats to the global ecological environment,has the characteristics of toxicity,concealment,hysteresis,accumulation,easy access to the food chain endangers human health.Phytoremediation is the most environmentally friendly one in the repair of heavy metal pollution.Sedums has the characteristics of wide adaptability,strong resistance,easy reproduction,and excellent ornamental characteristics.At the same time,they are easy to harvest and reusable for many years.Accordingly,the study included the response and accumulation of 3 sedums(Sedum spurium ’Fuldaglut’,Sedum hybridum ’Immergrunchen’ and Sedum’Herbstfreude’)to cadmium and lead stress,and the potential of artificial chelating agents combined with plants to repair Cd and Pb contaminated soil.Results can be concluded as follows:(1)After Cd stress treatment,3 sedums chlorophyll content and chlorophyll fluorescence parameters decreased to some extent,MDA content was significantly promoted.SOD activity,APX activity,soluble sugar,soluble protein content,PCs content to respond appropriately to mitigate the damage caused by Cd stress,and ultimately manifested in the morphological indicators,the growth indexes of the 3 sedums inhibition degree increased with the increase of Cd concentration,but no death occurred.Sedum hybridum ’Immergrunchen’ was highly tolerant plant,Sedum spurium ’Fuldaglut’ and Sedum ’Herbstfreude’ was moderately tolerant plant.The maximum Cd accumulation of 3 sedums(Sedum spurium ’Fuldaglut’,Sedum hybridum ’Immergrunchen’ and Sedum ’Herbstfreude’)was 33.52μg plant-1,51.08 μg plant-1,17.00 μg plant-1.(2)Under the Pb stress,the biomass of Sedum spurium ’Fuldaglut’ and Sedum ’Herbstfreude’ was inhibited to varying degrees,and Sedum hybridum ’Immergrunchen’ was promoted to varying degrees.The chlorophyll fluorescence parameters of 3 sedums were not significantly affected,the chlorophyll synthesis increased,and the MDA content increased significantly,but the antioxidant enzyme system and osmotic adjustment system responded positively to the Pb stress.The tolerance thresholds for Sedum spurium ’Fuldaglut’,Sedum hybridum ’Immergrunchen’ and Sedum ’Herbstfreude’ to Pb were 1000 mg-kg-1,2000 mg·kg-1 and 1500 mg-kg-1,respectively.The maximum Pb accumulation of 3 sedums(Sedum spurium ’Fuldaglut’,Sedum hybridum ’Immergrunchen’ and Sedum ’Herbstfreude’)was 1104.22 μg-plant-1,3056.04 μg-plant-1,275.95 μg·plant-1.(3)3 sedums resist the Cd and Pb stress through the combination of photosynthetic system,membrane system,antioxidant enzyme system and osmotic adjustment mechanism.Finally,the tolerance threshold of Sedum hybridum ’Immergrunchen’ was 25-500 mg kg-1,and the other 2 sedums were lower than 25-500 mg kg-1,and Sedum hybridum ’Immergrunchen’ was highly tolerant plant,Sedum spurium ’Fuldaglut’ and ’Herbstfreude’ were moderately tolerant plant.The maximum Cd accumulation of shoot in 3 sedums(Sedum spurium ’Fuldaglut’,Sedum hybridum ’Immergrunchen’ and Sedum ’Herbstfreude’)was 37.69 μg·plant-1,70.μ.g-plant-1,38.60 μg-plant-1,and the maximum Pb accumulation of shoot was 990.00μg plant-1,1930.41 μg·plant-1,200.98 μg plant-1.Sedum hybridum’Immergrunchen’ had the largest accumulation of Cd and Pb,and the maximum Cd and Pb of was achieved under the treatment of 100-1500 mg·kg-1.(4)The activity of Cd and Pb increased with the increase of GLDA and EDTA concentration,the antioxidant enzyme system,osmotic adjustment mechanism,PCs synthesis response positively,while the vacuolar segregation and cell wall retention were enhanced,they all can reduce the damage of Cd-Pb stress on Sedum hybridum ’Immergrunchen’.The difference in Cd chelating ability between GLDA and EDTA was small,when GLDA was 1.5 mmol kg-1 and EDTA was 6 mmol·kg-1,the maximum Cd accumulation of shoot was 145.27 μpg·plant-1and 142.65 μg plant-1,which was 1.49 and 1.48 times higher than that of the control.The chelating ability of GLDA to Pb was not only stronger than EDTA,and the amount was less than EDTA,the maximum Pb accumulation of shoot was 4589.36μg·plant-1、2885.87μg plant-1,which was 1.95 and 1.22 times higher than that of the control.Overall,GLDA was superior to EDTA.