Dipartimento di Biologia Vegetale dell'Università di Torino e Istituto per la Protezione delle Piante del CNR, Viale Mattioli 25 10125 Torino, Italy.
Am J Bot. 2011 Jul;98(7):1148-63. doi: 10.3732/ajb.1000486. Epub 2011 Jun 28.
We investigated whether four widespread, photosynthetic Mediterranean meadow orchids (Ophrys fuciflora, Anacamptis laxiflora, Orchis purpurea, and Serapias vomeracea) had either nutritional dependency on mycobionts or mycorrhizal fungal specificity. Nonphotosynthetic orchids generally engage in highly specific interactions with fungal symbionts that provide them with organic carbon. By contrast, fully photosynthetic orchids in sunny, meadow habitats have been considered to lack mycorrhizal specificity.
We performed both culture-dependent and culture-independent ITS sequence analysis to identify fungi from orchid roots. By analyzing stable isotope ((13)C and (15)N) natural abundances, we also determined the degree of autotrophy and mycoheterotrophy in the four orchid species.
Phylogenetic and multivariate comparisons indicated that Or. purpurea and Oph. fuciflora featured lower fungal diversity and more specific mycobiont spectra than A. laxiflora and S. vomeracea. All orchid species were significantly enriched in (15)N compared with neighboring non-orchid plants. Orchis purpurea had the most pronounced N gain from fungi and differed from the other orchids in also obtaining C from fungi.
These results indicated that even in sunny Mediterranean meadows, orchids may be mycoheterotrophic, with correlated mycorrhizal fungal specificity.
我们调查了四种广泛分布的、光合作用的地中海草地兰花（Ophrys fuciflora、Anacamptis laxiflora、Orchis purpurea 和 Serapias vomeracea）是否对菌根真菌具有营养依赖性或真菌特异性。非光合作用的兰花通常与真菌共生体进行高度特化的相互作用，这些共生体为它们提供有机碳。相比之下，阳光充足的草地生境中的完全光合作用兰花被认为缺乏菌根特异性。
我们进行了培养依赖和非培养的 ITS 序列分析，以鉴定兰花根中的真菌。通过分析稳定同位素（(13)C 和 (15)N）自然丰度，我们还确定了这四种兰花物种的自养和菌根异养程度。
系统发育和多变量比较表明，与 A. laxiflora 和 S. vomeracea 相比，Or. purpurea 和 Oph. fuciflora 的真菌多样性较低，菌根真菌谱更为特异。与邻近的非兰花植物相比，所有兰花物种均显著富集 (15)N。Orchis purpurea 从真菌中获得的 N 增益最为明显，与其他兰花不同的是，它还从真菌中获得 C。
这些结果表明，即使在阳光充足的地中海草地中，兰花也可能是菌根异养的，并且与相关的菌根真菌特异性有关。
