| In order to study the effects of rice straw substrate on the remediation of cadmium contaminated soil by plant,the physio-biochemical responses and accumulation characteristics of Brassica juncea L.to cadmium stress under rice straw substrate were studied with pot experiments by different treatments including the composition,thickness and additive of substrate and the concentration of cadmium,as well as the effects of using rice straw substrate to strengthen the growth and Cd enrichments of five plant species were compared.The results were as followed:?1?In treatments of Brassica juncea L.applied with different composition substrates?soil,rice straw,rice husk,fermented rice straw,fermented rice straw and rice husk?under 50 mg·kg-1 cadmium stress for 45 d,the activity of superoxide dismutase?SOD?were increased and the peroxidase?POD?and catalase?CAT?activites showed an alternate increasement trends,while the MDA and proline content changed little.Furthermore,the plant biomass and soil enzyme activity under the fermentation substrates were generally higher than those of the unfermented substrates.The application of soil,rice straw,rice husk,fermented rice straw,fermented rice straw and rice husk substrates could promote the cadmium enrichment of Brassica juncea L..Compared with the untreated group,the concentration of cadmium in the underground part s of plants increased by 40.51% and 50.32% 133.20%,140.43% and 96.69%,respectively.The concentration of cadmium on the aerial parts increased by 7.1 0%,35.12%,50.00%,52.30% and 47.22%,respectively.The fermented straw substrate can most effectively promote the growth and Cd enrichment of Brassica juncea L..In addition,the thickness of the substrate will also affect the cadmium tolerance and enrichment of Brassica juncea L.: the activities of SOD and CAT were enhanced,meanwhile,the maximal PS?efficiency?Fv/Fm?and photosynthetic efficiency?A?were increased significantly when the 2 cm substrates was applied under 50 mg·kg-1 cadmium stress,moreover,the cadmium enrichment concentration and biomass reached the maximum,compared with the non-substrate treatment,the biomass of the underground and aboveground parts increased by 20.32% and 135.82% respectively,and the concentration of cadmium increased by 140.43% and 52.30% respectively.While the POD and SOD activities decreased,the photosynthetic capacity was inhibited and the plant height,biomass and soil enzyme activity were also reduced when the thickness was increased.The 2 cm fermented straw substrate can most effectively promote the growth and enrichment of Brassica juncea L..The addition of bamboo charcoal powder significantly reduced the antioxidant enzyme activity and cadmium enrichment concentration of Brassica juncea L.,while the addition of slow release fertilizer or EM bacteria alone could not enhance the ability of cadmium enr ichment of the plant.The antioxidant enzyme activity and photosynthetic capacity of Brassica juncea L.were significantly increased when the substrate containing compound additive?bamboo charcoal powder 2% + slow release fertilizer 2% + EM 1%?was applied.Compared with the non-additive control group,the biomass of aboveground and underground areas increased by 58.92% and 68.35%,respectively,and the concentration of cadmium increased by 14.11% and 15.86%,respectively.Compared with the non-substrate control group,the biomass of aboveground and underground areas increased by 91.19% and 297.01%,respectively,and the concentration of cadmium increased by 73.80% and 178.55%,respectively.The composite additive substrate can most effectively promote the growth and enrichment of Brassica juncea L..The activity of SOD and CAT in Brassica juncea L.was enhanced,and the photosynthetic capacity,biomass,enrichment concentration and enrichment coefficient were increased by cadmium gradually enhanced with the increasing concentration of cadmium within a range from 0 to 50 mg·kg-1.However,the plant growth was inhibited significantly under the condition of high cadmium concentration(100 mg·kg-1),although the enrichment coefficient and transport coefficient o f the plants decreased,the cadmium enrichment concentration increased,meanwhile the soil enzyme activity increased at first and then decreased with the decrease of cadmium concentration.In summary,2 cm fermented straw substrate containing compound additive can effectively promote the growth and cadmium enrichment of Brassica campestris L.under cadmium contaminated soil conditions.?2?The responses of Brassica juncea L.,Brassica campestris L.,Helianthus annuus L.,Brassica napus L.and Amaranthus mangostanus L.to cadmium stress were not exactly the same,but in general,the 2 cm fermented straw substrate containing compound additive?bamboo charcoal powder 2% + slow release fertilizer 2% + EM 1%?was able to promote the growth and cadmium enrichment of several plants under the condition of cadmium stress.Compared with the control group,the concentration of cadmium in the roots of the five plants increased by 41.97%,23.75%,13.21%,73.18% and 7.82% respectively,and the enrichment of leaf cadmium increased by 109.80%,101.64%,48.62%,111.76% 71.57%,among which the growth of Amaranthus mangostanus L.and the cadmium enrichment of Brassica juncea L.were the most remarkable. |
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