Effects Of Clonal Integration On Microbial Processes And Community Composition In The Rhizosphere Of Glechoma Longituba

Habitat heterogeneity is ubiquitous under natural conditions and its presence willgreatly increase the difficulty of plants capturing or utilizing resources. Clonal plantspossess the ability to extensively share or translocate resources through stolon orrhizome between interconnected ramets, severing stolon or rhizome would lead todecrease the survival and vegetative propagation of ramets. The processes of theresources sharing and translocation are termed as physiological integration.Physiological integration as an important ecology advantage can ameliorate theselective stress caused by resources heterogeneity and increase survival and growth ofclonal plants, which facilitates to colonizing for heterogeneous environment or thegrowth of ramets in habitats with low resources availability.Photoassimilates assimilated by plants enter into soil via rhizodeposition and are amajor source of carbon, energy or structural material for heterotrophic microbes in soiland affect the degradation processes of soi organic matters (SOM) by microorganisms;SOM are decomposed as inorganic materials by soil microbes to the uptake andutilization of plants. In this study, we investigated the effects of clonal integration onmicrobial processes and community composition in the rhizosphere of offspringramets under heterogeneous light using a stoloniferous herb G. longituba. The rametpair was comprised of an mother ramet placed in full sun and an offspring onessubjected to80%shades. The stolon between mother ramet and offspring one waseither connected or severed. Simultaneously, we also measured the maximumphotosynthetic capacity of shaded offspring ramets to investigate the relationshipsbetween soil nitrogen transformation and carbon capture capacity of ramets, which isvery meaningful for revealing the ecological adptation of clonal integration. We haveobtained the following results:(1) Clonal integration significantly improved C, N availability and organic nitrogen mineralization rates in the rhizosphere of shaded offspring ramets. Clonalintegration significantly increased total organic carbon (TOC), dissolved organiccarbon (DOC) and nitrogen (DON) concentrations in the rhizosphere of shadedoffspring ramets. The increased TOC, DOC and DON concentrations facilitated toenhanced microbial growth and activities, thereby contributed to increasing CmicandNmicin the rhizosphere of shaded offspring ramets. Clonal integration ameliorated themineralization rate (Nmin) and nitrification rate (Nnitri) via enhancing extracellularenzymes activities involved in the decomposition of N from SOM, such asN-acetyl-β-D-glucosaminidase (NAGase) and urease, thus increasing inorganicnitrogen (NH4+-N and NO3--N) availability.(2) Clonal integration significantly increased the total phospholipid fatty acids(PLFAs) concentrations of microbial community. The similar pattern also was foundin bacterial, gram-positive bacterial, gram-negative bacterial and fungal (especiallyECM fungal) PLFAs concentrations in the rhizosphere of shaded offspring ramets. Aprincipal component analysis (PCA) of PLFAs concentrations revealed that microbialcommunity composition in the rhizosphere of shaded offspring ramets was clearlyaltered by clonal integration. Regression analysis among the PLFAs concentrations ofvarious microbial groups and total organic carbon (TOC), dissolved organic carbon(DOC), dissolved organic nitrogen (DON) and microbial processes displayed positiverelationships.(3) Clonal integration ameliorated the negative effects of heterogeneouslight-stress on offspring ramets growth performance. The Pn-PPFD and Pn-Cicurve ofconnected offspring ramets were higher than severed offspring ramets. Compared tosevered offspring ramets, connected offspring ramets displayed higher the contents ofleaf nitrogen and chlorophyll and allocated more leaf nitrogen to its photosyntheticmachinery under heterogeneous light, thus enhancing resources capture ability (Vcmaxand Jmax) and the accumulation of total biomass of shaded offspring ramets.Additionally, clonal integration significantly increased growth performance of shadedoffspring ramets and whole clonal fragments, but had no significant influences onexposed mother ramets.Clonal integration promoted the assimilation and uptake of N via improvingmicrobial processes and community composition in the rhizosphere of shadedoffspring ramets and incurred allocating more leaf nitrogen to its photosyntheticmachinery, thus promoting carbon gain capacity of clonal plants suffering fromheterogeneous light-stress and allowing their pre-acclimation to high-light conditions, which may facilitate to the opportunistic light-capture of these ramets. Based on adivision of labour mechanism, N could be translocated from shaded offspring rametsto exposed mother ones. Clonal integration may ameliorate carbon gain capacity ofclonal plants, which enhances their adaptability in temporal and spatial heterogeneoushabitats.