Umata Hidetaka, Gale Stephan W, Suetsugu Kenji, Ota Yuko
a Faculty of Agriculture, Kagoshima University.
c Kadoorie Farm and Botanic Garden.
Mycoscience. 2024 Mar 31;65(2):68-78. doi: 10.47371/mycosci.2023.12.002. eCollection 2024.
The degree of specificity between fully myco-heterotrophic (MH) orchids and mycorrhizal fungi is regarded as high, but some species undergo a mycobiont shift as they transition from juvenile to adult plant. We investigated morphological and physiological aspects of the interaction between the fully MH and its four known mycobionts to elucidate developmental consequences of variable, life-stage-dependent specificity. Of five randomly sampled germinated seeds co-cultured with each mycobiont, sp. '' colonized all, and colonized one, and subsp. colonized none. Whereas 16.2% of aseptically germinated seeds exhibited onward growth when co-cultured with , just 1.5-2.6% did so with the other species. Even so, colonized and formed internal rhizomorphs within rhizomes established with , suggesting that this mycobiont can replace and potentially can oust the latter. We infer that the orchid can associate with and mycobionts throughout its life, but that enhances early growth. However, because has a higher wood-rotting capacity than , rapid resource exhaustion may cause nutrient supply shortages. We hypothesize that secondary colonization by or species triggers displacement and that this mycobiont shift sustains orchid growth for longer.
完全菌根异养（MH）兰花与菌根真菌之间的特异性程度被认为很高，但有些物种在从幼苗过渡到成年植株的过程中会发生菌根共生体转变。我们研究了完全MH兰花与其四种已知菌根共生体之间相互作用的形态学和生理学方面，以阐明可变的、依赖生命阶段的特异性所产生的发育后果。在与每种菌根共生体共同培养的五粒随机采样的萌发种子中，sp. '' 定殖了所有种子， 定殖了一粒种子，而subsp. 未定殖任何种子。当与 共同培养时，16.2%的无菌萌发种子表现出进一步生长，而与其他物种共同培养时，只有1.5 - 2.6%的种子如此。即便如此， 在与 建立的根状茎中定殖并形成了内部根状菌索，这表明这种菌根共生体可以取代并可能驱逐后者。我们推断，这种兰花在其整个生命周期中都可以与 和 菌根共生体建立联系，但 能促进早期生长。然而，由于 的木材腐烂能力比 更强，资源的快速耗尽可能会导致养分供应短缺。我们推测， 或 物种的二次定殖会引发 被取代，并且这种菌根共生体转变能使兰花生长更长时间。
