McCormick Melissa, Burnett Robert, Whigham Dennis
Smithsonian Environmental Research Center, Edgewater, MD 21037, USA.
Plants (Basel). 2021 Jun 20;10(6):1251. doi: 10.3390/plants10061251.
Mycorrhizal fungi are critical to understanding the distribution patterns of many plants, but they are especially important for orchids. Some orchids may change the mycorrhizal fungi they use through their lives, either in response to changes in abiotic or biotic conditions, or as a result of ontogenetic changes that alter the orchid's need for fungal nutrition. The temperate terrestrial orchid germinates only on decomposing wood, but often persists well after the wood has completely decomposed and has been incorporated into the soil. We used PCR and Sanger sequencing to ask: (1) Do mature retain protocorm fungi or are protocorm and adult mycorrhizal fungi mutually exclusive? (2) Are protocorm fungi limited to areas with decomposing wood? (3) Does the abundance of protocorm fungi in the substrate differ between decomposing wood and bare soil? We found that retained protocorm fungi into maturity, regardless of whether they were growing in persistent decomposing wood or soil. Protocorm fungi were not restricted to decomposing wood but were more common and abundant in it. We conclude that the mycorrhizal fungi associated with change during the ontogeny of individuals. These results highlight the importance of assessing protocorm fungi, in addition to mycorrhizal fungi associating with adult orchids, to understand the conditions needed for orchid germination, growth, and reproduction.
菌根真菌对于理解许多植物的分布模式至关重要，但对兰花而言尤为重要。一些兰花在其生命周期中可能会改变所利用的菌根真菌，这要么是对非生物或生物条件变化的响应，要么是由于个体发育变化改变了兰花对真菌营养的需求所致。温带地生兰花仅在正在分解的木材上发芽，但在木材完全分解并融入土壤后通常仍能良好生长。我们使用聚合酶链反应（PCR）和桑格测序法来探究：（1）成熟植株是否保留原球茎真菌，还是原球茎真菌和成年植株的菌根真菌相互排斥？（2）原球茎真菌是否仅限于有正在分解的木材的区域？（3）在正在分解的木材和裸露土壤中，基质中原球茎真菌的丰度是否存在差异？我们发现，无论植株是生长在持续分解的木材中还是土壤中，都会保留原球茎真菌直至成熟。原球茎真菌并不局限于正在分解的木材，但在其中更为常见且丰度更高。我们得出结论，与植株个体发育相关的菌根真菌会发生变化。这些结果凸显了在了解兰花发芽、生长和繁殖所需条件时，除了评估与成年兰花相关的菌根真菌外，评估原球茎真菌的重要性。
