Effects Of Chelating Agents On The Absorption And Accumulation Of Heavy Metal Pb In Hemp(cannabis Sativa L.)

In recent years,study on phytoremediation of heavy metal contaminated soil has become a hot topic in environmental governance at home and abroad,that is,the use of some super-accumulated or highly-tolerant plants to absorb and transfer some heavy metals from the soil.High-biomass tolerant plants have the disadvantages of low heavy metal absorption efficiency,so chelating agents can be applied to the soil to make heavy metal ions into an effective state that is easy for plants to absorb,thereby promoting the absorption and accumulation of heavy metals by plants,and ultimately reducing soil The purpose of medium heavy metal content.However,chelating agents may cause damage to plants and the environment to a certain extent,and different chelating agents have different effects on promoting the absorption of heavy metals by plants.Therefore,it is of great significance and potential application value to search for suitable species and concentrations of chelating agents to assist plants in absorbing soil heavy metals.In this paper,Yunma 1（Y1）,Bamahuoma（BM）,Yunma 7（Y7）,Yunwan 6（YW6）,Jinma 1（J1）,Wanma 1（W1）and Qingma 1（Q1）seven hemp varieties were used as research materials.Paper culture method was used for germination test and pot method was used at seedling stage（Pb（NO₃）²was mixed with the soil to simulate heavy metal lead contamination）.Seed germination parameters,seedling growth and physiological indicators,and plant heavy metal lead content.The effects of chelating agents on lead tolerance and absorption and accumulation of heavy metal Pb in hemp were evaluated.The main results are as follows:（1）Under different concentrations of EDTA-2Na and citric acid（CA）stress,the germination indicators of the seven hemp varieties were more consistent.With the increase of EDTA-2Na concentration,the germination potential,germination rate,radicle length and germ length of the seven hemp varieties were lower than those of the control.The difference was significant under high concentration EDTA-2Na treatment;the low concentration of CA treatment had little effect on the hemp seed germination index,and significantly promoted BM and Q1,at high concentration,the hemp germination index was significantly reduced.（2）With the increase of the concentration of EDTA-2Na,the plant height,stem diameter and biomass of Y1 and BM gradually decreased;low concentration of CA could promote the growth of Y1 and BM,but high concentrations of CA produced toxic effects on the plants.Low concentrations of EDTA-2Na and CA can alleviate the toxicity of heavy metal Pb to the plants,and thus increase the plant height,stem thickness,and biomass compared to the pure heavy metal treatment group.（3）The application of EDTA-2Na or CA alone increased the malondialdehyde（MDA）content in Y1 and BM leaves as a whole,while the chlorophyll content was significantly lower than the control;low concentrations of chelating agents could alleviate the leaves caused by heavy metal lead stress The MDA content increased;the SOD and POD contents of Y1 leaves both decreased with increasing chelating agent concentration,while the SOD and POD containing activities of BM leaves increased first and then decreased with increasing chelating agent concentration.The application of the chelating agent led to a decrease in the soluble protein content of Y1 and BM leaves,but at a low concentration,it could alleviate the decrease in soluble protein content due to heavy metal Pb.（4）EDTA-2Na and CA promoted the absorption of heavy metal Pb by hemp.The Pb content in hemp increased first and then decreased with the increase of the concentration of chelating agents.Compared with the control group that only added heavy metal Pb,the application of chelating agent The Pb content in hemp increased by 1.23-11.59 times,and the Pb accumulation increased by 1.04-67.77 times.When the concentration of chelating agent was 2-10 mmol·kg^-1,the Pb enrichment coefficient and The transfer coefficients were all greater than 1,which increased by 60.25%-79.49%compared with the control group containing only heavy metal Pb,indicating that the chelating agent significantly increased the ability of hemp to enrich and transfer heavy metal Pb;low concentration chelating agents could improve the resistance of hemp The coefficient makes the hemp have higher tolerance to high concentration of Pb;the CA-treated hemp has improved resistance to Pb,and the EDTA-2Na-treated hemp has enhanced Pb accumulation ability.In summary,the application of the test chelators with high concentration had certain negative impact on the growth of industrial hemp,but the low-concentration of chelators could alleviate the toxicity of heavy metal Pb to hemp and enhance the absorption and accumulation of heavy metal Pb in hemp.