ABSTRACT Mycoheterotrophic plants are non-photosynthetic plants that obtain nutrients from fungi. Even though most of these plants are associated with the mycorrhizal partners of surrounding photosynthetic plants, recent studies have suggested that some mycoheterotrophic orchids indirectly obtain carbon from decaying organic matter through associations with saprotrophic fungi. However, such suggestions have been based primarily on indirect evidence, such as the 13C and 15N abundances of fungi and plants. It was recently reported that some mycoheterotrophs yield elevated Δ 14C values, owing to the indirect acquisition of 14C-enriched bomb carbon from dead wood. The approach was based on the anthropogenic change of Δ 14C values; atmospheric CO2 were globally elevated by nuclear weapons testing in the 1950s and early 1960s, but have steadily declined since its peak after the atmospheric nuclear test ban treaty of 1963. The study has provided novel evidence that mycoheterotrophic plants can exploit both mycorrhizal and saprotrophic fungi. We suggest that the radiocarbon analysis is also useful for investigating the nutritional modes of mixotrophic plants as well as for investigating whether the recruitment of wood-decaying fungi into novel mycorrhizal partnerships preceded the evolution of full mycoheterotrophy.

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使用放射性碳评估真菌异养植物的菌根状态

摘要 真菌异养植物是从真菌中获取营养的非光合植物。尽管这些植物中的大多数都与周围光合植物的菌根伙伴有关，但最近的研究表明，一些真菌异养兰花通过与腐生真菌的联系从腐烂的有机物质中间接获取碳。然而，这些建议主要基于间接证据，例如真菌和植物的 13C 和 15N 丰度。最近有报道称，由于从死木中间接获得了富含 14C 的炸弹碳，一些真菌异养菌产生了升高的 Δ 14C 值。该方法基于 Δ 14C 值的人为变化；1950 年代和 1960 年代初期的核武器试验使全球大气中的二氧化碳升高，但自 1963 年禁止大气核试验条约达到顶峰以来一直在稳步下降。该研究提供了新的证据，表明真菌异养植物可以利用菌根真菌和腐生真菌。我们建议放射性碳分析对于研究混合营养植物的营养模式以及研究木材腐烂真菌是否在完全真菌异养进化之前招募到新的菌根伙伴关系中也很有用。