The Tolerance Of The Potential Herbaceous Energy Plants To Cadumiun Stress Associated With Cell Metabolism

Remediate Cd-contaminated soils is becoming a serious problem worldwide.Remediating heavy metal-contaminated farm soil and ensuring food security and ecological health has become an urgent need for all countries to achieve sustainable development.Using excellent germplasm resources of energy plant as research object will be an effective way to improve the economic benefits of environmental remediation and to promote regional economic development.We used potential herbaceous energy plants P.frutescens、Datura stramonium and tobacco for our study.Through laboratory simulation experiments,the tolerance and enrichment characteristics,physiological and metabolic responses of seedlings under cadmium stress were explored.It is of great significance for mining its utilization value.The seeds of Perilla frutescens（L.）Britt.、Datura stramonium L.and Nicotiana tabacum L.（5 genotypes）were selected.Seeds were first cultivated in the substrate for 66 days,and then the seedlings of robust and consistent were transplanted into Hoagland solution for growth.After 7 days,the seedlings were transferred to nutrient solution containing Cd Cl₂,and Cd treatments were 0,1,10,20 and 40mg/L,respectively.Each treatment has14 strains.The seedlings were randomly arranged.Samples were harvested at 7 days after the test treatment.By measuring the growth status of seedlings（plant height,root length,fresh weight）and cadmium content in tissues,the characteristics of its tolerance and accumulation of cadmium were characterized.Analyze the changes in tissue oxidative stress（ROS,MDA）,antioxidant capacity（SOD,POD,CAT,GSH,Pro,etc）and photosynthesis（chlorophyll a,b and total content）to reveal the physiology response to cadmium stress;Furthermore,using histocytochemical staining techniques,the effects of cadmium stress on the morphology of tissue cells（stained using Safranin/Fast Green）and the secretion and accumulation of main secondary metabolites of phenols（Fast Blue BB staining）and alkaloids（Dragendorffs test）,aimed at revealing its metabolic response to cadmium stress.The main results of this research are shown below:1.The plant height,root length,and fresh weight of the seven materials all decreased to varying degrees under cadmium stress.Among them,P.frutescens has the weakest tolerance to cadmium,Datura stramonium has the strongest tolerance to cadmium,and tobacco was in between.2.Among the seven materials in this study,although the transport coefficient is less than 1,the cadmium enrichment amount and the enrichment coefficient all meet the standards of hyperaccumulator plants,which suggests that they can be used as potential remediation plants for cadmium contaminated soil.The enrichment capacity,enrichment coefficient,and transport coefficient of different materials under the same concentration of cadmium stress are different,and even different genotypes of tobacco are also quite different.The results of this study show that the cadmium accumulation capacity of tobacco is significantly stronger than P.frutescens and Datura stramonium.Among the five genotypes of tobacco,NDY-2 has the strongest cadmium accumulation capacity,and the weakest is NDY-3.3.The ability of the same material to absorb,accumulate and transport cadmium under different concentrations of cadmium stress will also be different.When the cadmium stress concentration is 1mg/L,the enrichment ability of tobacco NDY-4 is the strongest;when the cadmium stress concentration is 20mg/L,the enrichment ability of tobacco NDY-1 is the strongest;when the cadmium stress concentration is 40mg/L,tobacco NDY-2 had the strongest enrichment ability.Therefore,different varieties can be selected for remediation according to the degree（mild、moderate、severity）of soil pollution.4.GSH content,Pro content,and POD activity of the seven materials increased under cadmium stress.From this,we posit that the three compounds might play a significant role for increased plant resistance.MDA content of tobacco NDY-1、NDY-4 was significantly increased（P<0.05）under cadmium stress.Significant decrease in chlorophyll content of tobacco NDY-1、P.frutescens was observed upon exposure to cadmium stress（P<0.05）.5.Phenols are mainly distributed in roots and leaves,and alkaloids are mainly distributed in leaves.Under cadmium stress,the phenolic substances and alkaloids of the seven materials showed an overall upward trend.This suggests that the main secondary metabolites may play an important role in plant anti-adversity.In summary,the energy plants P.frutescens、Datura stramonium and tobacco show strong tolerance and enrichment of heavy metal cadmium,which may be related to their physiological and metabolic responses to cadmium stress.It has certain development and utilization value in the remediation of cadmium contaminated in soil.Different tobacco genotypes have different tolerance and enrichment ability under cadmium stress.In the actual restoration process,different genotypes of the same variety should be screened.In the seven materials of this study,the cadmium concentration in the shoots was lower than the cadmium content in the roots,which prevented the transfer of cadmium to the shoots and reduced the toxicity to the shoots.This may be one of Cd tolerance mechanism.