Effects Of Tetracycline Stress To Physiology And Secondary Metabolites In Houttuynia Cordata Thunb.

Nowadays,antibiotics,as a new type of organic pollutants,have had serious adverse effects on the ecological environment and human health.The shadow of antibiotics has appeared in livestock and poultry industry,medicine industry and aquaculture industry.The environmental problems caused by the widespread use or abuse of antibiotics and improper disposal have become the hot research topics in recent years.As the most populous developing country,the laws of antibiotics are not perfect in China,and antibiotics are widely detected in different media in the environment.The plant growth in the environment cannot be separated from soil.In plant soil ecosystem plants,soil and soil microorganisms,material exchange is carried out all the time.The residual antibiotics in the soil enter into the plant and microorganism through this process,which will affect the metabolism behavior and physical and chemical properties of plants and microorganisms.As one of the most widely used and most used antibiotics,tetracycline antibiotics(TCs)are urgently needed to study their toxicity and regulation strategies to the environment.In this paper,tetracycline(TC)was used as the representative of antibiotics,and Houttuynia cordata Thunb.was used as the experimental object.MS medium and soil were used as the medium to establish the system of H.cordata MS medium and Houttuynia soil system.The chlorophyll,superoxide dismutase(SOD),peroxidase(POD)and pod were systematically studied in different habitats.The effects of catalase(CAT),malondialdehyde(MDA)and main phenols were studied to investigate the response mechanism of H.cordata to TC plant toxicity.Meanwhile,the rhizosphere bacterial community of H.cordata was used as a biological factor,and then it was purified and then artificially recombined and added to two sterile systems.The physical and chemical indexes of H.cordata were analyzed by experiments,and the effect of bacterial community on the response of TC stress was discussed.The behavior strategies of soil microorganisms in stress environment were analyzed by monitoring the indicators of ammonium nitrogen,available phosphorus and available potassium.It provides effective theoretical support for understanding and controlling the potential risks of antibiotic toxicity.The results show that:(1)In MS medium,TC stress could increase the MDA content,decrease the chlorophyll content and increase SOD,POD and CAT activities.In sterile MS medium,MDA content of H.cordata.leaves in each experimental group was always higher than CK;chlorophyll content was always lower than CK;except for 0.016 g/L at 12 ～ 18 d,SOD activities of each experimental group was higher than CK in other stages;POD activities of each experimental group was always higher than CK;except for 0.004 g/L at 12 d and 0.01 g/L at 24 d,CAT activities of each experimental group was higher than CK in other stages.In MS medium with bacteria,TC stress could increase the MDA content,and the MDA content in each experimental group did not increase significantly compared with CK at 6 ～ 18 d,and 30 d,MDA content in each experimental group was significantly higher than that of CK(P < 0.05);except for 0.004 g/L at6 d and 0.016 g/L at 30 d,the chlorophyll content in each experimental group was lower than that of CK in other periods;SOD activities in each experimental group was always higher than that of CK;except 0.004 g/L at 24 d,0.01 and 0.016 g/L at 30 d,POD activities was higher than that of CK in other periods;CAT activities was higher than that of CK at 6 and 24 d.(2)In sterile MS medium,TC stress could inhibit the synthesis of phenols in H.cordata leaves.Except for 0.01 g/L at 6 d,chlorogenic acid content in all experimental groups was less than that of CK,and rutin content in all experimental groups was always less than that of CK;except for 0.01 and 0.016 g/L TC at 6 ～ 12 d,afodougoside content in all experimental groups was less than that of CK;isoquercitrin content in all experimental groups was always less than that of CK;except for 0.01 and0.016 g/L TC at 6 d,quercitrin content in all experimental groups was less than that of CK.In MS medium with bacteria,except chlorogenic acid,TC had no significant inhibitory effect on the synthesis of phenols in the early stage of the experiment,and phenols content in each experimental group was less than that in CK at the end of the experiment.Under 0.01 g/L and0.016 g/L TC stress,chlorogenic acid content decressed;rutin content was less than CK at 24 ～ 30 d;under 0.01 g/L and 0.016 g/L TC stress,aloposide content was less than CK at 24 ～ 30 d,isoquercitrin content less than CK at 24 ～ 30 d;quercetin content less than CK at 30 d.(3)In sterile soil,TC stress increased MDA content,chlorophyll content and SOD,POD and CAT activities of H.cordata leaves.In soil with bacteria,under 0.016 g/kg TC stess MDA content was greater than CK,and MDA content of each experimental group was greater than CK under 0.016 g/kg TC stress at 18 ～ 30 d;under 0.004,0.01 and 0.016 g/kg TC stress,chlorophyll content was less than CK at 12,18 d,and greater than CK at 6,24 and 30 d;compared with CK,under 0.004,0.01 and 0.016g/kg TC stress SOD activities increased;except 0.016 g/kg at 6 and 18 d,0.004 g/kg at 12 d,POD activities was higher than CK,except 0.004 g/kg at 12 d,CAT activities was greater than CK.In natural soil,TC stress resulted in MDA content greater than CK,and chlorophyll content less than CK,SOD and POD activities greater than CK,and CAT activities was greater than CK after 18 days.(4)In three kinds of soil medium,compared with CK,0.004,0.01 and0.016 g/kg TC stress resulted in decrease of phenols in H.cordata leaves.In sterile soil,rutin and quercetin content were less than CK,while chlorogenic acid,aforoside and isoquercetin were less than CK at 24 ～ 30 d.In the soil with bacteria,chlorogenic and alfrescein content were less than CK,while rutin was less than CK at 18 ～ 30 d,isoquercetin and quercetin were less than CK at 12 ～ 30 d.(5)The bacteria in fishy rhizosphere affect the physiology and secondary metabolism of H.cordata.The results showed that: compared with CK,the CAT activities of H.cordata leaves was inhibited,MDA contents was decreased and the Isoquercitrin contents was increased in the MS medium with bacteria at 6 ～ 18 d,while in the MS medium the CAT activities was increased,the MDA content was increased and the Isoquercitrin content was decreased without bacteria at 6 ～ 18 d.The results showed that: compared with the CK,the chlorogenic acid contents of H.cordata leaves decreased and the quercitrin content increased in the bacteria soil at 6 d,while the chlorogenic acid content of H.cordata leaves increased and the quercitrin content decreased in the soil without bacteria at the 6d.