BACKGROUND The shade represents one of the major environmental limitations for turfgrass growth. Shade influences plant growth and alters plant metabolism, yet little is known about how shade affects the structure of rhizosphere soil microbial communities and the role of soil microorganisms in plant shade responses. In this study, a glasshouse experiment was conducted to examine the impact of shade on the growth and photosynthetic capacity of two contrasting shade-tolerant turfgrasses, shade-tolerant dwarf lilyturf (Ophiopogon japonicus, OJ) and shade-intolerant perennial turf-type ryegrass (Lolium perenne, LP). We also examined soil-plant feedback effects on shade tolerance in the two turfgrass genotypes. The composition of the soil bacterial community was assayed using high-throughput sequencing. RESULTS OJ maintained higher photosynthetic capacity and root growth than LP under shade stress, thus OJ was found to be more shade-tolerant than LP. Shade-intolerant LP responded better to both shade and soil microbes than shade-tolerant OJ. The shade and live soil decreased LP growth, but increased biomass allocation to shoots in the live soil. The plant shade response index of LP is higher in live soil than sterile soil, driven by weakened soil-plant feedback under shade stress. In contrast, there was no difference in these values for OJ under similar shade and soil treatments. Shade stress had little impact on the diversity of the OJ and the LP bacterial communities, but instead impacted their composition. The OJ soil bacterial communities were mostly composed of Proteobacteria and Acidobacteria. Further pairwise fitting analysis showed that a positive correlation of shade-tolerance in two turfgrasses and their bacterial community compositions. Several soil properties (NO3--N, NH4+-N, AK) showed a tight coupling with several major bacterial communities under shade stress. Moreover, OJ shared core bacterial taxa known to promote plant growth and confer tolerance to shade stress, which suggests common principles underpinning OJ-microbe interactions. CONCLUSION Soil microorganisms mediate plant responses to shade stress via plant-soil feedback and shade-induced change in the rhizosphere soil bacterial community structure for OJ and LP plants. These findings emphasize the importance of understanding plant-soil interactions and their role in the mechanisms underlying shade tolerance in shade-tolerant turfgrasses.

中文翻译：

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遮荫胁迫对草坪草形态生理和根际土壤细菌群落的影响。

背景技术阴影代表草皮草生长的主要环境限制之一。阴影会影响植物的生长并改变植物的新陈代谢，但对于阴影如何影响根际土壤微生物群落结构以及土壤微生物在植物阴影响应中的作用知之甚少。在这项研究中，我们进行了温室试验，研究了遮荫对两种对比遮荫草皮（耐荫矮秆草皮（Ophiopogon japonicus，OJ）和不耐荫的多年生草皮型黑麦草（黑麦草（LP）。我们还研究了两种草皮草基因型的土壤植物反馈对耐荫性的影响。使用高通量测序分析土壤细菌群落的组成。结果在遮荫胁迫下，OJ比LP维持较高的光合作用能力和根系生长，因此发现OJ比LP更耐荫。不耐荫的LP对耐荫和土壤微生物的反应要优于耐荫OJ。遮荫和活土减少了LP的生长，但是增加了生物量分配给活土中的芽。在荫蔽胁迫下，土壤植物反馈减弱，导致活土中LP的植物遮荫响应指数高于无菌土壤。相反，在相似的阴影和土壤处理下，OJ的这些值没有差异。荫罩压力对OJ和LP细菌群落的多样性影响不大，反而影响了它们的组成。OJ土壤细菌群落主要由变形杆菌和酸性细菌组成。进一步的成对拟合分析表明，两种草皮草的耐荫性与其细菌群落组成呈正相关。几种土壤特性（NO3--N，NH4 + -N，AK）在阴影胁迫下与几种主要细菌群落紧密耦合。此外，OJ共享已知的核心细菌类群，可促进植物生长并赋予其遮荫胁迫的耐受性，这提示了OJ-微生物相互作用的共同原理。结论土壤微生物通过植物-土壤反馈和阴影诱导的OJ和LP植物根际土壤细菌群落结构的变化来介导植物对阴影胁迫的响应。这些发现强调了理解植物-土壤相互作用及其在耐荫草坪草中耐荫机理中的作用的重要性。