Ecotoxicological Effects Of Oxytetracycline And 4-epi-oxytctracyclinc On The Seedling Development Of Chinese White Cabbage

Oxytetracycline(Oxytetracycline,OTC)is a kind of tetracycline antibiotics,which is widely used in daily life.However,in animal husbandry,livestock and animal for oxytetracycline cannot completely absorb or metabolize,most to oxytetracycline parent compounds or their metabolites excreted in the form of oxytetracycline and degradation products of livestock manure in the biological activity still exists,even in certain conditions can be reduced to maternal oxytetracycline.Among them,4-(4-epi-Oxytctracyclinc,EOTC)is a degradation product of oxytetracycline.However,the effects of tetracycline antibiotics on plants are only limited to the study of surface layer,and there are few studies on OTC and EOTC,especially the toxicity of EOTC to plants.Aiming at the above problems,based on the black soil as tested soil,Chinese cabbage as tested plants,to investigate the effects of physiological and biochemical indexes of OTC and EOTC on Chinese cabbage seedlings,changes of ultrastructure observation of Chinese cabbage root and mesophyll cells,determine the residues of OTC and EOTC in Chinese Cabbage by LC/MS,evaluate in response to OTC and EOTC stress of Chinese cabbage,the main conclusions are as follows:(1)in response to OTC and EOTC the germination of Chinese cabbage seeds:OTC and EOTC concentration was low,Chinese cabbage seed germination potential and germination rate but no significant effect at high concentration(>50 mg·L-1)could significantly inhibit the germination rate and germination potential.The results showed that the germination rate and germination potential of OTC and EOTC were inhibited at the concentration of 50 mg·L-1.(2)Chinese cabbage seedling height and root length of OTC and EOTC in response to:OTC and EOTC is the first to promote the inhibitory influence of plant height for Chinese cabbage seedlings,which increased OTC and EOTC concentration reached 100 mg·kg-1,the plant height difference compared with the control of Chinese cabbage significantly.The root length of pakchoi was inhibited,and the higher the concentration,the stronger the inhibition.The effects of low concentration and high concentration on the fresh weight of Chinese cabbage seedlings were inhibited.The results showed that under low concentration treatment,the tolerance of Chinese cabbage was better,and the inhibitory effect of oxytetracycline and oxytetracycline on pakchoi was less than that of Chinese cabbage.(3)the response of Chinese cabbage seedlings chlorophyll and carotenoid of OTC and EOTC:OTC and EOTC of Chinese cabbage in vivo chlorophyll a,chlorophyll b and total carotenoids were inhibited,and with oxytetracycline and difference to oxytetracycline concentration increased,the inhibition effect is more obvious.Moreover,the inhibition rate of chlorophyll and carotenoid was higher,the leaf senescence was faster,and the toxicity was stronger.The results showed that when the plants were exposed to stress,the chloroplasts were injured,resulting in the decrease of chlorophyll content and the inactivation or degeneration of the enzymes related to photosynthesis.(4)the response of antioxidant system of Chinese cabbage seedlings of OTC and EOTC:effects of OTC on POD activity was first promoted after inhibition,EOTC always inhibited the activity of POD;OTC for the activity of CAT showed inhibition,EOTC in low concentration(5 mg·L-1,),the activity of CAT slightly promoted,but the difference is not obvious,while reducing CAT activity concentration.Compared with oxytetracycline,4-epi-Oxytctracyclinc had a greater effect on CAT activity.OTC and EOTC can promote the activity of SOD.The results showed that the antioxidant defense ability of Chinese cabbage seedlings was inhibited by OTC and EOTC stress.(5)the response of other resistance factors to OTC and EOTC in Chinese Cabbage Seedlings:the effects of OTC and EOTC on soluble sugars were promoted.OTC and EOTC showed a trend of increasing and then decreasing to soluble protein.OTC and EOTC had no significant effect on the proline content in Pakchoi at low concentration,at high concentrations(100 mg·kg-1),under OTC and EOTC stress,the free proline increased 73.81%and 85.39%.The content of MDA in OTC and EOTC was increased with the increase of concentration.The results show that the plant will produce a series of stress responses under stress.(6)the changes of the microstructure of Chinese Cabbage Seedlings:the membrane system of plant cell membrane and many kinds of organelles were damaged by the excessive amount of oxytetracycline and oxytetracycline.The changes of the submicroscopic structure of Chinese cabbage were mainly the changes of plant cell wall,chloroplast and mitochondria.The results showed that oxytetracycline and oxytetracycline could interfere with the cell structure and function,and thus lead to toxic effects on plants.(7)OTC and EOTC accumulation in Chinese cabbage in vivo:with the increase of oxytetracycline concentration in soil,accumulation of leaf and root in Chinese cabbage has gradually increased,and the antibiotic content in roots of Chinese cabbage was higher than the content of Chinese cabbage leaves.From the enrichment and migration coefficients in general,<to oxytetracycline oxytetracycline,and with the increase of OTC and EOTC concentration,and the difference to the enrichment coefficients of terramycin oxytetracycline decreased gradually,and the enrichment coefficients of most<1 test.The reason for this result may be that,because the Chinese cabbage seedlings only culture 7d,the growth time is short,and is the soil culture method,the absorption is small,so the enrichment coefficient is small.In addition,the plant is very smart,start self defense mechanism,the concentration of the body will not continue to rise with the increase in the concentration of external pollutants.