Ecological toxicity of antibiotics on the germination of Medicago sativa

【Objective】 This study explored the effects of oxytetracycline,sulfadiazine and ofloxacin residues in livestock manure on the germination and seeding growth of Medicago sativa to understand the ecotoxicological effects of these three drugs on forage crops and to provide a scientific basis for the evaluation of the effects of antimicrobials in livestock and poultry excreta on ecological security.【Method】 Ahydroponic method was used with seven concentrations of each antibiotic0(CK),0.1,0.5,1.0,5.0,10.0 and 50.0 μg/mLto analyze their effects on germination characteristics,seedling growth and chlorophyll content in M. sativa.【Results】 Oxytetracycline at ≥ 50.0 μg/mL significantly inhibited the seed germination of M. sativa(P<0.05),while the other two drugs had no significant effect(P>0.05). Sulfadiazine promoted greater plant height at ≤ 0.5 μg/mL,while the other drugs had a significant inhibitory effect on the root length and,to a lesser extent,plant height of seedlings at higher concentrations(5.0-50.0 μg/mL). Different concentrations of oxytetracycline increased the dry weight of M. sativa seedlings,while increases were observed with sulfadiazine and ofloxacin only at lower concentrations(≤ 1.0 μg/mL);higher concentrations(>5.0 μg/mL)caused decreases. Sulfadiazine and oxytetracycline caused larger decreases in seedling water content with increasing concentration,while ofloxacin caused the water content to decrease at lower concentrations but water content increased at higher concentrations. The three antibiotics caused decreases in chlorophyll content in the order of ofloxacin>sulfadiazine>oxytetracycline. The chlorophyll content of oxytetracycline and ofloxacin decreased with increasing concentration.【Conclusion】 Sulfadiazine and ofloxacin have little effect on M. sativa germination at all concentrations tested,whereas high concentrations of oxytetracycline inhibited germination.The three antibacterial drugs have different effects on root length,plant height,dry weight,water content and chlorophyll,with the main deleterious effects being the inhibition of root length,plant height and chlorophyll synthesis.