克隆整合对遮荫白夹竹分株根际土壤细菌生物特征的影响

摘要

克隆整合被认为是克隆植物维持生态优势的重要手段,其通过分株间生理整合缓解资源异质性带来的压力.文章以根状茎克隆植物白夹竹(Phyllostachys bissetii为研究对象,探讨异质性光照下克隆整合对白夹竹分株根际土壤细菌生物特征的影响.白夹竹克隆片段包含一个近端分株(proximal ramet)和一个远端分株(distal ramet),近端分株或远端分株分别置于80％遮荫环境,另一分株置于全光照环境;同时,分株间根状茎保持连接或割断处理.研究结果表明,不论白夹竹克隆片段近端分株遮荫还是远端分株遮荫,克隆整合均显著促进了遮荫分株根际土壤溶解性有机碳(DOC)含量和微生物生物量碳、氮含量(MBC,MBN);根状茎连接条件下遮荫分株根际土壤胞外N-乙酰基-β-氨基葡萄糖苷酶(NAGase)、脲酶(Urease)活性显著高于根状茎割断处理的遮荫分株;对遮荫分株根际土壤基因组DNA的16S rDNA V3、V4可变区的测序结果表明,可操作分类单元(OTUs)归于13个门,415个属.与根际土壤氮素转化相关的菌群Nitrosomonadaceae (uncultured),Nitrospira,Nitrospinaceae (uncultured),Xanthobacteraceae (uncultured),Bradyrhizobium相对丰度较小(最高值为11.8％).基于OTUs的主成分分析(PCA)表明,根状茎割断处理并没有对遮荫分株根际土壤细菌生物群落结构产生显著性影响.克隆整合显著促进了遮荫分株根际土壤C有效性,进而刺激了微生物调控的土壤有机质(SOM)周转过程.克隆整合对异质生境下克隆植物土壤细菌生物特征的影响可能部分解释了克隆植物的生态优势.%Clonal integration plays an important role for clonal plants during adaptation to heterogeneous habitats,by enhancing the survival of clonal fragments,thus,improving growth performance.An in-situ experiment was conducted using a clonal fragment of Phyllostachys bissetii with two successive ramets.We focused on microbial properties in the rhizosphere soil of shaded,distal,or proximal ramet.Shading (80％ shading) was applied to distal or proximal ramets,respectively,whereas counterparts were placed in full sunlight.The rhizome between two successive ramets was either severed or retained intact.In present study,dissolved organic carbon (DOC),microbial biomass,and two extracellular enzymes (N-acetyl-β-D-glucosaminidase,urease) were investigated in the rhizosphere soil of shaded distal and proximal ramets.The composition of the soil microbial community in the rhizosphere of shaded distal and proximal ramets was confirmed.The key results of this study are as follows:DOC in the rhizosphere soil of shaded distal or proximal ramets was significantly increased by clonal integration.Furthermore,increased microbial biomass carbon and nitrogen (MBC,MBN) were observed in the rhizosphere soil of shaded distal and proximal ramets.Clonal integration significantly enhanced the activities of N-acetyl-β-D-glucosaminidase (NAGase) and urease in the rhizosphere soil of shaded distal and proximal ramets.A total of 556519 reads and 18898 OTUs were obtained from the 12 soil samples through Illumina Miseq sequencing.The bacterial OTUs were assigned into 13 different phyla and 415 genera.Nitrosomonadaceae (uncultured),Nitrospira,Nitrospinaceae (uncultured),Xanthobacteraceae(uncultured),Bradyrhizobium were associated with soil N cycling,with low relative abundance.The results of principal component analysis revealed that the effect of clonal integration on the composition of the soil microbial community in the rhizosphere of shaded distal and proximal ramets were not significant,sharing similar microbial diversity at the OTU level.In summary,C availability and soil microbial biomass were significantly increased by clonal integration in the rhizosphere soil of shaded distal and proximal ramets and further stimulated the turnover of soil organic matter mediated by soil microbes in the rhizosphere.We tentatively conclude that the effect of clonal integration on soil microbial properties in the rhizosphere soil may partly explain the important ecological advantage of clonal plants,especially the species subjected to heterogeneous light habitats.