The plant endosphere is colonized by complex microbial communities and microorganisms, which colonize the plant interior at least part of their lifetime and are termed endophytes. Their functions range from mutualism to pathogenicity. All plant organs and tissues are generally colonized by bacterial endophytes and their diversity and composition depend on the plant, the plant organ and its physiological conditions, the plant growth stage as well as on the environment. Plant‐associated microorganisms, and in particular endophytes, have lately received high attention, because of the increasing awareness of the importance of host‐associated microbiota for the functioning and performance of their host. Some endophyte functions are known from mostly lab assays, genome prediction and few metagenome analyses; however, we have limited understanding on in planta activities, particularly considering the diversity of micro‐environments and the dynamics of conditions. In our review, we present recent findings on endosphere environments, their physiological conditions and endophyte colonization. Furthermore, we discuss microbial functions, the interaction between endophytes and plants as well as methodological limitations of endophyte research. We also provide an outlook on needs of future research to improve our understanding on the role of microbiota colonizing the endosphere on plant traits and ecosystem functioning.

中文翻译：

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植物内圈世界——植物内的细菌生命

植物内圈被复杂的微生物群落和微生物定殖，它们至少在其生命周期的一部分时间内定殖在植物内部，并被称为内生菌。它们的功能范围从共生到致病。所有植物器官和组织通常都被细菌内生菌定植，它们的多样性和组成取决于植物、植物器官及其生理条件、植物生长阶段以及环境。植物相关微生物，尤其是内生菌，最近受到高度关注，因为人们越来越意识到宿主相关微生物群对其宿主功能和性能的重要性。一些内生菌功能主要是通过实验室检测、基因组预测和少数宏基因组分析得知的；然而，我们对在植物活动中，特别是考虑到微环境的多样性和条件的动态。在我们的评论中，我们介绍了有关内圈环境、其生理条件和内生菌定植的最新发现。此外，我们还讨论了微生物功能、内生菌与植物之间的相互作用以及内生菌研究的方法学局限性。我们还提供了对未来研究需求的展望，以提高我们对定植于内圈的微生物群对植物性状和生态系统功能的作用的理解。