中文摘要：

植物根系与菌根真菌形成的互惠共生体，即菌根（mycorrhizas）是最常见、最广泛分布的共生体之一。自然条件下，一些植物的根系可同时形成由2种类型菌根构成的混合菌根，或菌根与细菌、菌根与放线菌、菌根与其他种类真菌构建的所谓复合共生体。文中从复合共生体的概念入手，简要介绍混合菌根、菌根与细菌、菌根与放线菌、菌根与其他真菌构建的复合共生体的多样性、形态解剖特征、生长发育及其功能等方面的研究概况，旨在为推进该领域的研究提供依据和借鉴的思路。

英文摘要：

The symbionts, mycoerrhizas formed on plant roots, are most popular and are distributed wide- ly in various ecosystems. Under natural conditions, some plants may form ecto- and endomycorrhiza or dual mycorrhiza, and dual symbionts formed between mycorrhiza and bacteria, mycorrhiza and actino- myces, and mycorrhiza and the other fungi. The present article firstly introduces the concept of dual sym- bionts, and briefly shows the diversity, morphologic characteristics, growth and function of the dual sym- bions formed with mycorrhizal fungi, bacteria, actinomyces or the other fungi on roots of plants, in order to provide the basis and idea for promoting the study on dual symbionts.