| The driving mechanism of plant secondary metabolites is always the focus and difficulty in the field of plant basic research.Scientists have carried out a lot of research work on it,proposed many metabolic pathways and possible impact factors,and carried out practical verification.However,the driving mechanism of phenotypic variation in plant secondary metabolic compounds still needs to be solved urgently.Therefore,this paper that,taking Houttuynia cordata Thunb.as the research object,using tissue culture technology to eliminate external differences,whether the phenotypic variation in secondary metabolic compounds of H.cordata are mainly determined by their own genes or external environment was clarified,changes in soil environment and soil microorganisms were also identified,and the environmental driver factors of phenotypic variation in H.cordata secondary metabolites was explored.The main results are as follows:1.Screening the tissue culture conditions of H.cordata.The results showed that the underground stem of H.cordata was sterilized by 75% medical alcohol for 30 s and 0.1% mercury solution for 10 min.The best start-up culture of underground stem segment was MS medium of 2 mg/L KT or 1 mg/L 6-BA+3 mg/L KT,strong seedling culture was MS medium of 2.0 mg/L KT,and the best MS medium of underground stem was MS medium of 0.5 mg/L 6-BA+1.5 mg/L NAA.2.To compare the accumulation of phenolics and volatiles in H.cordata from the same source by tissue culture,laboratory culture and wild culture.The results showed that the changes of phenolic and volatile substances in H.cordata were different,but the overall changes were laboratory culture > wild culture > tissue culture,which implied that the effects of culture conditions on phenolic and volatile substances in H.cordata were significantly greater than that of genetic factors.3.To analyze the rhizosphere environmental characteristics of H.cordata cultivated in laboratory and in situ.The results showed that soil p H increased,and the contents of organic matter(OM),total nitrogen(TN)and available nitrogen(AN)decreased before laboratory culture than after;background value of soil enzymes activities in laboratory culture was larger than that of in situ culture,and the changes of rhizosphere soil enzymes activities before and after in laboratory culture from Baiyun(BY)and Renhuai(RH)sample plots were inconsistent.The organic acids in the rhizosphere soil of H.cordata were mainly oxalic acid and the content of oxalic acid rhizosphere soil of H.cordata in situ soil culture was significantly lower than that in laboratory culture.4.To analyze the rhizosphere soil microorganism characteristics of H.cordata cultivated in laboratory and in situ.The results showed that the ? diversities of soil bacterial were significantly richer than fungal.The compositions of bacterial and fungal communities in situ culture plots were similar,and the compositions of bacterial and fungal communities in laboratory culture were similar.After laboratory cultivation of H.cordata from RH,the Ace,Chao I,Shannon and Simpson index of soil bacteria were increased and tended to the bacterial community structures in situ cultivation;the Ace and Chao I index of soil fungal were decreased,while the Shannon and Simpson index were increased,and tended to the fungal community structures in situ cultivation,suggesting the ? diversity of soil bacterial were increased,the richness of fungal were decreased but the diversity were increased,and the community structures of bacteria and fungal in soil was affected due to the participation of H.cordata plants.5.To analyze the correlation between phenolics of H.cordata and rhizosphere soil characteristics.The results showed that there was a significant positive correlated between quercitrin and soil p H(P < 0.05),while other phenolics was not significantly correlated with physicochemical properties of rhizosphere soil,p H and oxalic acid.Chlorogenic acid,afzelin,isoquercitrin,quercitrin and quercetin of H.cordata were no significantly correlated with soil ureases,Phosphatase and sucrase activities.And there was no significant correlation with the OTUs,Ace,Chao I,Shannon and Simpson indices of soil microorganisms,which may be due to the counteraction of physicochemical properties of soil,p H,oxalic acid and microorganism to accumulation of H.cordata phenolics.6.To analyze the correlation between volatiles of H.cordata and rhizosphere soil characteristics.The results showed that ?-pinene,camphene,?-myrcene,limonene,cis-3-hexene-1-ol were significantly negatively correlated with total potassium(TK)(P<0.05),while linalool were significantly positively correlated with TK(P<0.05).The ?-pinene,limonene,cis-3-hexene-1-ol,camphene and ?-pinene were extremely significantly or significantly positively correlated with AN(P<0.01 or P<0.05).trans-2-hexenal was extremely significantly positively correlated with the available Phosphorus(AP)(P<0.01);cis-3-hexenyl-acetate was significantly negatively correlated with p H(P<0.05),while linalool was significantly positively correlated with soil p H(P<0.01),cis-3-hexenyl-acetate was significantly positively correlated with TN and Phosphatase(P<0.05);Decanal was significantly negatively correlated with total phosphorus(TP)(P<0.05);?-Pinene,camphene,?-pinene,limonene and cis-3-hexene-1-ol were significantly positively correlated with oxalic acid(P<0.05),while linalool was significantly negatively correlated with oxalic acid(P<0.05);?-Myrcene,trans-2-hexenal,hexanol,decanal,?-caryophyllene,2-undecanone and borneol were significantly correlated with OTUs,Ace,Chao I indices of bacterial(P<0.05);?-Pinene,camphene,?-pinene,?-myrcene,cis-3-hexenyl-acetate,cis-3-hexen-1-ol and linalool were significantly correlated with OTUs,Ace and Chao I indices of fungal(P<0.05),while ?-myrcene,trans-2-hexenal,hexanol,trans-2-Hexen-1-ol,decanal,linalool,2-undecanone and borneol were significantly correlated with Shannon and Simpson indices(P<0.05),suggesting that soil microorganisms might affect accumulation of volatiles in H.cordata. |
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