The Effect Of Leifsonia Naganoensis RE3-4 On Lead/Cadmium Adsorption And Phragmites Australis Growth-Promoting

Due to the ability of nitrogen fixation,growth promotion,diseases resistance,heavy metal resistance and pollutants degradation,endophytes can secrete certain substances to promote plant growth,to decontaminate the pollutants indirectly.It also can be directly applied to the pollutant removal,because of its resistance and adsorption function.In this study,the biological characteristics and application mechanism of a Phragmites australis endophytes—Leifsonia naganoensis RE3-4 were explored.The mechanism of how RE3-4 to promote the growth of reed was revealed by studingthe synthesis of auxin and tolerance of heavy matals.The Langmuir and Freundlich adsorption isotherm curve were fitted,in order to compare the adsorption ability of strain RE3-4 on Pb/Cd.The sodium alginate bead which can prevent wash away and recycle were manufactured,to strengthen the capacity of adsorbing Pb and Cd.Adopted the SEM(-EDX)、FT-IR analysis method,to reveal inner mechanism of adsorbing Pb and Cd by strain RE3-4.The main conclusions were as follows:(1)Under the existence of L-tryptophan,strain RE3-4 had the ability of synthesizing auxin analogues—indole acetic acid(IAA).Comparing with IAA standard,biosynthetic IAA significantly improved the reed seedlings growth,and the optimum growth concentration was 1.0 mg/L.(2)Strain RE3-4 had the ability of resisting heavy metal,and comparing the tolerance of strain on metal ions,the result showed that strain RE3-4 was more tolertant to Pb than Cu and the tolertance of Cd was weakest.The different levels of lead in culture medium made the different growth of the reed seeds,which infected by strain RE3-4,and to a certain extent(concentration of lead less than 400 mg/kg),strain RE3-4 can improve germination rate of the coerced reed seeds and promote root length of seedling.(3)The results of fitting adsorption isotherm curve suggested that the strain RE3-4 can adsord Pb and Cd.Protein played a most important role in the process of adsorption,phospholipids were in a secondary role,polysaccharides,amino acids and other substances also adsorbed metal ions.Strain RE3-4 produced the tolerance to lead and cadmium ions by damage,fracture,aggregation and deformation of cells.(4)The adsorption balance of Pb or Cd by Na-Alg bead achieved in the condition of which the pH of aquatic solution was 5.0 and operation time was 8 hours.The fouctional groups of O-H,C-H and C-0 were interacted with Pb/Cd ion during the adsorption process,and the polysaccharides area also might adsorb certain amount of Pb/Cd.The covalent bonding,crystal precipitation and ion exchange reaction occurred on the bead surface to reduce the contents of metal ions in aquatic solution.The Na-Alg beads had secondary adsorption to Pb or Cd after desorption,and in this way,it possessed preferable recycling performance.