Partial mycoheterotrophy is more widespread among orchids than previously assumed
Partial mycoheterotrophy is more widespread among orchids than previously assumed
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DOI：
10.1111/nph.13865
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发表时间：
2016-07-01
期刊：
影响因子：
9.4
通讯作者：
Gebauer, Andreas C.
中科院分区：
文献类型：
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作者：
Gebauer, Gerhard;Preiss, Katja;Gebauer, Andreas C.
兰科植物被认为是地球上种类最多、分布最广的植物科(Merckx等人，2013年)，几乎在所有大洲的每个生境都有880属22 000种兰科植物。所有兰花都会产生微小的尘埃状种子(Arditti&Gami，2000)，这需要碳(C)和菌根真菌提供的养分才能萌发和幼苗发育的早期阶段(Smith&Read，2008)。这种营养被称为初始真菌异质营养(Merckx，2013)。后来，大多数兰花长出绿叶，进行光合作用，但仍保持菌根状态。然而，也有200种非绿叶兰花。这些兰花需要菌根真菌提供完整的碳和矿物质营养，被称为完全异养真菌(Leake，1994；Merckx，2013)。由于它们利用富含13C(Gleixner等人，1993)和15N真菌(Gebauer&Dietrich，1993)的真菌来源，与来自相同微生境的自养植物相比，真菌异养兰花的13C和15N显著丰富(Gebauer&Meyer，2003；Trudell等人，2003；Hynson等人，2013)。根据它们在自养非兰花和非绿叶兰花之间的同位素定位，在过去的十年里，发现了几种叶绿素兰花从自养光合作用产物和相关真菌中获得碳(Gebauer&Meyer，2003；Hynson等人，2013)。这种混合营养的碳获取模式被称为部分真菌异养(Gebauer&Meyer，2003；Merckx，2013)。过去，碳稳定同位素自然丰度的使用在阐明高等植物从两个来源获得碳的过程中发挥了重要作用。当两种感兴趣的碳源在其同位素组成上有足够的区别时，这种方法是非常成功的，例如，在C3光合作用的半寄生虫的情况下，同时利用寄主植物的C4或CAM光合作用(Press等人，1987；Schulze等人，1991；Ziegler，1996)。这种方法的局限性出现在两个潜在的碳源在碳同位素组成上没有充分区分的情况下，例如在利用C3寄主植物的C3半寄生虫的情况下(Schulze等人，1991年；Ziegler，1994年)。自Bernard(1909)的早期研究以来，大多数绿叶兰花被认为与属于根尖菌属系统发育异质性组合的真菌形成菌根(Dearnaley等人，2012年)。有趣的是，所有已知的部分真菌异养兰花都与同时形成外生菌根的真菌另外或唯一相关。
With> 22 000 species in 880 genera occurring on all continents in almost every habitat, the Orchidaceae is considered the most diverse and most widely distributed plant family on Earth (Merckx et al., 2013). All orchids produce tiny, dust-like seeds (Arditti & Ghani, 2000) that require carbon (C) and nutrient supply by mycorrhizal fungi for germination and in the early seedling development phase (Smith & Read, 2008). This kind of nutrition is called initial mycoheterotrophy (Merckx, 2013). Later the majority of orchids develop green leaves and photosynthesize, yet remain mycorrhizal. There are, however, also> 200 achlorophyllous orchid species. These orchids require complete C and presumably mineral nutrient supply from mycorrhizal fungi and are known as full mycoheterotrophs (Leake, 1994; Merckx, 2013). Owing to their use of a 13C-(Gleixner et al., 1993) and 15N-enriched (Gebauer & Dietrich, 1993) fungal source for nutrition, mycoheterotrophic orchids are significantly enriched in 13C and 15N, when compared with autotrophic plants from the same microhabitats (Gebauer & Meyer, 2003; Trudell et al., 2003; Hynson et al., 2013). Based on their isotopic positioning between autotrophic nonorchids and achlorophyllous orchids, during the last decade a couple of chlorophyllous orchids have been found to acquire C from both autotrophic photosynthates and associated fungi (Gebauer & Meyer, 2003; Hynson et al., 2013). This mode of mixotrophic C gain is called partial mycoheterotrophy (Gebauer & Meyer, 2003; Merckx, 2013).In the past, the use of C stable isotope natural abundance played an important role in elucidating C gain by higher plants from two origins. This approach was highly successful when the two C sources of interest were sufficiently distinguished in their isotope composition, for example, in the case of hemiparasites with C3 photosynthesis simultaneously utilizing host plants with C4 or CAM photosynthesis (Press et al., 1987; Schulze et al., 1991; Ziegler, 1996). Limitations of this approach emerged in cases with two potential C sources not sufficiently distinguished in their C isotope composition, for example in the case of C3 hemiparasites utilizing C3 host plants (Schulze et al., 1991; Ziegler, 1994). Since early investigations by Bernard (1909), the majority of chlorophyllous orchids are considered as forming mycorrhizas with fungi that belong to the phylogenetically heterogeneous assemblage of rhizoctonias (Dearnaley et al., 2012). Interestingly, all known partially mycoheterotrophic orchids are additionally or exclusively associated with fungi that simultaneously form ectomycorrhizas