间作大葱对桔梗根系分泌物的影响

Effects of Intercropping Allium fistulosum on Root Exudates of Platycodon grandiflorum

为探究间作大葱有效消减桔梗连作障碍的机理,本试验选取桔梗连作5年的地块进行研究,设置桔梗单作、大葱单作和桔梗大葱间作行比3∶2、4∶2、5∶2共5个处理,利用原位取土法收集不同处理的根际土,并进行根系分泌物的提取与GC-MS分析。结果表明,单作桔梗和桔梗大葱间作根系分泌物中2,2′-亚甲基双-(4-甲基-6-叔丁基苯酚)相对含量高达23.51%~39.63%,而且桔梗大葱间作根系分泌物中该物质相对含量显著高于单作桔梗和单作大葱;间作大葱提高桔梗根系分泌物中角鲨烯、β-谷甾醇、岩皂甾醇等抗胁迫物质和苯并噻唑、2-甲硫基苯并噻唑这类杀菌抑菌物质的相对含量,同时提高桔梗根系分泌物中喹啉、二苄胺、N-(1,3-二甲基丁基)-N′-苯基对苯二胺等碱性物质的相对含量,降低三十六烷、N,N-二甲基十二酰胺、苯乙烯、十五烷、十七烷相对含量,有效改善间作土壤微环境。综上所述,间作大葱改变了间作体系中桔梗根系分泌物的组成成分和相对含量,增加了桔梗根系分泌物中生长促进型化感物质的相对含量,降低抑制型化感物质的相对含量,改善间作桔梗根际微环境,有效消减桔梗连作障碍。

To clarify the alleviating mechanism of continuous cropping obstacle of Platycodon grandiflorum intercropped with Allium fistulosum,the plot of continuous cropping for 5 years was selected in this experiment.There were five treatments:P.grandiflorum monoculture,A.fistulosum monoculture,and intercropping of P.grandiflorum with A.fistulosum at row ratio of 3∶2,4∶2 and 5∶2.The rhizosphere soil of different treatments was collected by in situ soil sampling method,and the root exudates were extracted and analyzed by GC-MS.The results showed that the relative content of 2,2′-methylene bis-(4-methyl-6-tert-butylphenol)in root exudates of P.grandiflorum was 23.51%~39.63%,and that was significantly higher in the intercropped P.grandiflorum than that in monoculture.The relative contents of squalene,beta-sitosterol,saponin sterol,benzothiazole and 2-methylthiobenzothiazole in intercropped P.grandiflorum increased,and the relative contents of quinoline,dibenzylamine,N-(1,3-dimethylbutyl)-N′-phenylp-phenylene-diamine also increased,while the relative contents of hexatriacontane,N,N-dimethyldodecamide,styrene,pentadecane and heptadecane decreased,which effectively changed the soil microenvironment of intercropping.In conclusion,P.grandiflorum intecropped with A.fistulosum changed the component and relative content of root exudates of P.grandiflorum,increased contents of growth-promoting allelochemicals and decreased that of inhibiting allelochemicals,thus improving the rhizosphere microenvironment and effectively alleviating the cropping obstacle of P.grandiflorum.