Germplasm Screening And Utilization Potential For The Remediation Of Cadmium-contaminated Soil

Cadmium pollution is the most serious among the heavy metal pollutants that cause pollution to farmland soil in China.Cadmium can affect the biomass and quality of plants through its transfer and accumulation in the soil-plant system,thus affecting food safety and seriously threatening human health.Phytoremediation is an economical and effective soil remediation technology,which can reduce or remove heavy metal pollutants in soil.Compared with common plants,if some plants have large biomass,high tolerance and strong enrichment ability,they are more valuable for remediation.However,hyperaccumulator have the disadvantages of small biomass and low economic value.Therefore,the utilization of energy plants and aromatic plants is of great significance to improve the economic benefits of contaminated soil remediation and promote the development of regional economy.In this study,the potential energy plant of tobacco(Nicotina tabacum L.)and the aromatic plant basil(Ocimum Basilicum L.)were taken as the research objects.We chose two cultivated varieties of tabacco(NLY-1 and THY-2)and a native cultivar of basil,then studied the tolerance and enrichment capacity and physiological response(including oxidative stress,antioxidant effect,photosynthesis,etc.)of seedlings to Cd,and effects of Cd on foliar glandular hair density and substance metabolism at different concentrations of cadmium stress(0,1mg/L,20mg/L,40mg/L).Through the laboratory simulation test,the potential of remediation of contaminated soil was preliminarily evaluated,which laid the foundation for the future field remediation experiment.The main findings are as follows:1.For tobacco NLY-1,THY-2 and basil seedlings treated with different concentrations of cadmium,the growth status(including plant height,fresh weight and root length)was compared.The results showed: with the increase of cadmium concentration,three materials all can grow normally without death,but their growth were inhibited to different degrees.The inhibition of plant height of the three materials were NLY-1>THY-2>basil.The inhibition of fresh weight were THY-2>basil>NLY-1.The inhibition of taproot were NLY-1>THY-2>basil.The degree of inhibition to lateral roots depended on the concentration,at 1mg/L,THY-2>NLY-1>basil,at 20mg/L and 40mg/L,THY-2>NLY-1>basil.At different concentrations of cadmium,the three materials also appeared toxic symptoms of different degrees.NLY-1 had no obvious toxic symptoms under three concentrations of cadmium.THY-2 and basil had no obvious toxic symptoms at 1mg/L,but they appeared chlorosis and etiolation of different degrees at 20mg/L and 40mg/L,and the toxicity of THY-2 was more serious than basil.2.Aboveground tissue and root tissue were extracted from seedlings treated with different concentrations of cadmium,and then determined their content of cadmium,analyzed their BCF and TF.The results showed: with the increase of cadmium concentration,cadmium contents of both aboveground and root tissue increased in two kinds of tobacco(P<0.01),and they are greater than 100mg/kg,and BCF>1,TF<1.Their cadmium contents in the aboveground of basil increased firstly and then decreased with the increase of cadmium concentration(P<0.05).At 1mg/L,basil’s cadmium content in the ground is less than 100mg/kg,and it’s more than 100mg/kg at20mg/L and 40mg/L.The cadmium content in the underground part increased with the increase of cadmium concentration(P<0.01),and it’s more than100mg/kg,BCF>1,TF<1.To sum up,these three materials have a certain degree of tolerance and enrichment capacity at different concentrations of cadmium,and have a certain degree of utilization value.3.Observing physiological response(such as oxidative stress,antioxidant response,photosynthesis,etc.),glandular hair density and staining of main metabolite(alkaloids and phenol)of seedlings after treatment with different concentrations of cadmium,the results showed that,with the increase of the concentration of cadmium,the ROS content in NLY-1,THY-2 and basil were higher than the control,but there was no significant difference compared with the control.The activities of the three antioxidant enzymes(SOD,POD,CAT)all increased with the increase of cadmium concentration,and the three antioxidant enzyme activities of NLY-1 were more significantly affected(P<0.05).The content of GSH increased with the increase of cadmium concentration,but had no significant difference with the control,indicating that the response effect of GSH content to cadmium stress was not obvious in the three materials.Cadmium stress also inhibited the photosynthetic pigment content of seedlings,and the inhibitory effect on the photosynthetic pigment of NLY-1 was the most significant(P<0.05).From the changes in the content of proline and MDA,it can be seen that among the three plant materials,the membrane system of tobacco was more severely damaged.At 1mg/L,NLY-1>THY-2.At 20mg/L and 40mg/L,THY-2>NLY-1.For three plant materials,the observation of glandular hair density showed that Cd can effect more significantly NLY-1 leaves’ foliar glandular hair density(P<0.01).And the stain of glandular hair metabolites showed that the accumulation of metabolite(alkaloids and phenolic)in glandular hair increased to varying degrees,which may enhance the adaptability of seedlings in cadmium stress environment.Its molecular and cellular mechanisms need to be studied in depth.