Department of Biology, University of Copenhagen, Copenhagen, Denmark.
FEMS Microbiol Ecol. 2010 Nov;74(2):336-45. doi: 10.1111/j.1574-6941.2010.00956.x. Epub 2010 Aug 16.
The majority of herbaceous plants are connected by arbuscular mycorrhizal (AM) fungi in complex networks, but how this affects carbon (C) and phosphorus (P) allocation among symbionts is poorly understood. We utilized a monoxenic AM system where hyphae from donor roots colonized two younger receiver roots of varying C status. AM fungal C allocation from donor to receiver compartments was followed by measuring the (13)C contents in fungal- and plant-specific lipids, and P movement from a hyphal compartment was traced using (33)P. Four times more (13)C was translocated from donor to C-limited receiver roots, but C remained in fungal tissue. Root C status did not influence the overall AM colonization, but arbuscule density was twice as high in non-C-limited roots, and they received 10 times more (33)P. The number of hyphal connections between compartments did not influence C and P allocation. Interestingly, there were more fungal storage lipids, but fewer structural lipids inside C-limited roots. Our results indicate that AM colonization may poorly reflect host quality as C can be supplied from neighboring roots. A mycocentric view of the symbiosis is proposed where C-delivering hosts are resource islands for the exchange of P for C, and C-limited hosts are storage units.
大多数草本植物通过丛枝菌根（AM）真菌形成复杂的网络连接，但这种连接如何影响共生体之间的碳（C）和磷（P）分配尚不清楚。我们利用了一种单生 AM 系统，其中供体根系的菌丝定植在两个具有不同 C 状态的年轻受体根系中。通过测量真菌和植物特异性脂质中（13）C 的含量，以及使用（33）P 追踪菌丝室中的 P 运动，我们追踪了 AM 真菌从供体到受体室的 C 分配。从供体向 C 限制受体根转移的（13）C 量增加了四倍，但 C 仍留在真菌组织中。根 C 状态并不影响总体 AM 定殖，但在非 C 限制根中，丛枝密度高两倍，它们接收的（33）P 量多十倍。隔室之间的菌丝连接数量并不影响 C 和 P 的分配。有趣的是，C 限制根内的真菌储存脂质更多，但结构脂质较少。我们的结果表明，AM 定殖可能不能很好地反映宿主质量，因为 C 可以从邻近的根供应。提出了一种以真菌为中心的共生观点，其中提供 C 的宿主是交换 P 以获取 C 的资源岛，而 C 限制宿主是储存单元。
