基质湿度对黄芪幼苗防御应答及根际微生物的影响

Effects of Matrix Moisture on Defense Response and Rhizosphere Microbial Communities of Astragalus membranaceus var.mongholicus Seedlings

通过考察基质湿度对黄芪幼苗防御应答及根际微生物的影响,了解土壤水分在黄芪药材品质形成中的可能作用。采用渗灌控水方式控制盆栽黄芪基质水分,分光光度法测定黄芪幼苗根、茎、叶绿叶挥发物(green leaf volatiles,GLVs)合成途径关键酶——脂肪氧合酶(lipoxygenase,LOX)和苯丙烷类类物质合成关键酶——苯丙氨酸解氨酶(phenylalanin ammonia-lyase,PAL)活性和总黄酮含量,梯度稀释法测定根际细菌和真菌数量,SPSS软件进行数据分析。结果表明,高水分含量(81.6%)导致黄芪幼苗根际微生物数量显著下降,叶PAL和根LOX活性显著升高,但根中的总黄酮含量明显低于低湿度组的。相比较而言,低湿度组黄芪根际真菌和细菌数量无明显变化,且叶LOX活性较高。基质水分含量是影响黄芪黄酮合成与积累的重要因素,高基质湿度不利于黄芪黄酮类物质的合成与积累且很可能与根中高LOX活性有关,低基质湿度下较为稳定的根际微生物群落很可能是黄芪幼苗中黄酮类物质的合成与积累的有益因素。

To find out potential role of soil water on quality formation of Astragali Radix by exploring effects of matrix moisture on defense response and rhizosphere microbial communities of Astragalus membranaceus var. rnongho seedlings. The matrix moisture was controlled by the method of root-sphere osmotic irrigation, isoflavone content and activities of lipoxygenase （LOX） and phenylalanin ammonia-lyase （PAL） involved in the biosynthese of green leaf volatiles （GLVs） and isoflavones respectively, were determined by spectrophotometry; colony forming units （CFU） of rhizosphere bacteria and fungi were counted by gradient dilution method, resulting data was analyzed by SPSS software. Results： Higher matrix moisture （81.6 %） not only resulted in significant decrease in both rhizo- sphere bacterial and fungal CFUs and significant increase in leaf PAL and root LOX activities but lead to lower isoflavone content in roots. Comparatively, lower matrix moisture resulted in higher leaf LOX activities and relatively steady rhizosphere microbial communities and their CFUs were at the same level to the ones before planting. Matrix moisture affected the biosynthesis and accumulation of isoflavone compounds, and higher moisture adverse to the process, which might be caused by higher root LOX activity. Steady rhizosphere microbial communities in lower moisture level might benefit to the biosynthesis and accumulation of isoflavones.