ETH Zurich, Institute of Agricultural Sciences, Plant Nutrition Group, Eschikon 33, 8315, Lindau, Switzerland.
TSBF-CIAT, Tropical Soil Biology and Fertility Institute, c/o ICRAF, UN Avenue, Gigiri, PO Box 30677-00100, Nairobi, Kenya.
Mycorrhiza. 2011 Nov;21(8):689-702. doi: 10.1007/s00572-011-0371-5. Epub 2011 Apr 7.
Many studies have scrutinized the nutritional benefits of arbuscular mycorrhizal associations to their host plants, while the carbon (C) balance of the symbiosis has often been neglected. Here, we present quantification of both the C costs and the phosphorus (P) uptake benefits of mycorrhizal association between barrel medic (Medicago truncatula) and three arbuscular mycorrhizal fungal species, namely Glomus intraradices, Glomus claroideum, and Gigaspora margarita. Plant growth, P uptake and C allocation were assessed 7 weeks after sowing by comparing inoculated plants with their non-mycorrhizal counterparts, supplemented with different amounts of P. Isotope tracing ³³P and ¹³C) was used to quantify both the mycorrhizal benefits and the costs, respectively. G. intraradices supported greatest plant P acquisition and incurred high C costs, which lead to similar plant growth benefits as inoculation with G. claroideum, which was less efficient in supporting plant P acquisition, but also required less C. G. margarita imposed large C requirement on the host plant and provided negligible P uptake benefits. However, it did not significantly reduce plant growth due to sink strength stimulation of plant photosynthesis. A simple experimental system such as the one established here should allow quantification of mycorrhizal costs and benefits routinely on a large number of experimental units. This is necessary for rapid progress in assessment of C fluxes between the plants and different mycorrhizal fungi or fungal communities, and for understanding the dynamics between mutualism and parasitism in mycorrhizal symbioses.
许多研究都仔细研究了丛枝菌根共生体对其宿主植物的营养益处，而共生体的碳（C）平衡往往被忽视。在这里，我们提出了量化丛枝菌根共生体与三种植株（Medicago truncatula 与 Glomus intraradices、Glomus claroideum 和 Gigaspora margarita）之间的 C 成本和磷（P）吸收益处的方法。通过比较接种植物和非菌根植物在播种后 7 周时的生长、P 吸收和 C 分配情况，并用不同量的 P 进行补充。使用同位素示踪法（³³P 和 ¹³C）分别量化了菌根的益处和成本。G. intraradices 支持最大的植物 P 吸收并产生高 C 成本，这导致与接种 G. claroideum 的植物生长益处相似，G. claroideum 虽然在支持植物 P 吸收方面效率较低，但也需要较少的 C。G. margarita 对宿主植物施加了大量的 C 需求，但提供的 P 吸收益处微不足道。然而，由于植物光合作用的汇强刺激，它并没有显著降低植物的生长。像这里建立的这样一个简单的实验系统应该允许在大量实验单元上常规量化菌根的成本和益处。这对于评估植物与不同菌根真菌或真菌群落之间的 C 通量的快速进展以及理解菌根共生体中互惠共生和寄生之间的动态关系是必要的。
