Orchids are among the most popular flowers, admired for their beauty and delicate appearance. But beneath the surface, some orchids hide a darker secret: they live as parasites, stealing nutrients from fungi instead of producing their own food. Researchers from Kobe University investigated why this happens.
Most plants generate their own food through photosynthesis. However, some orchids take an alternative approach. These mycoheterotrophic plants tap into underground fungal networks, absorbing carbon and nutrients instead of producing their own. As a result, they lose the ability to photosynthesize and instead siphon resources from fungi.
Kenji Suetsugu and Hidehito Okada recently studied an orchid called Oreorchis patens, a partial parasite. This means the orchid can produce its own food but also takes up resources from fungi.
“I noticed that Oreorchis patens sometimes grows unusual coral-shaped rootstalks, a trait reminiscent of orchids fully relying on fungi. I thought that this would allow me to compare plants with these organs to those with normal roots, quantify how much extra nutrients they might be gaining, and determine whether that extra translates into enhanced growth or reproductive success,” says Suetsugu.
The study revealed that when Oreorchis patens grows near decaying wood — where fungi are more abundant — the orchids extract significantly more nutrients from them. But rather than reducing their reliance on photosynthesis, they use this extra energy to produce more flowers.
“In short, these orchids aren’t merely substituting for diminished photosynthesis, they’re boosting their overall nutrient budget. This clear, adaptive link between fungal parasitism and improved plant vigor is, to me, the most thrilling aspect of our discovery, as it provides a concrete ecological explanation for why a photosynthetic plant might choose this path,” says Suetsugu.
Opportunistic orchids
Unlike most plants that form mutually beneficial relationships with fungi (where the fungi provide nutrients and receive sugars in return), mycoheterotrophic orchids exploit their fungal partners. The fungi these orchids parasitize are often mycorrhizal fungi, which usually form symbiotic relationships with trees.
In these normal partnerships, the fungi help trees absorb nutrients from the soil, and in return, trees provide the fungi with sugars. However, parasitic orchids hijack this system, taking nutrients from the fungi without giving anything back.
Beyond this, Oreorchis patens may be parasitizing decomposer fungi instead of those that help living trees. This way they access nutrients from dead organisms rather than living hosts.
This parasitic approach seems to be effective. The study found that orchids relying more on fungi were healthier, with taller flowering stalks and more blossoms. This also suggests that fungal-derived carbon is not just a backup plan — it provides a major advantage under the right conditions.
However, this dependence on fungi is not without risks. The fungi Oreorchis patens rely on are only abundant in environments with ample decaying wood. If the right fungi are not present, the orchids may struggle to obtain enough nutrients. This might explain why not all individuals emphasize parasitism and why individuals retain the ability to photosynthesize.
An unseen network
The research on Oreorchis patens sheds light on an often-overlooked aspect of plant life: the hidden underground network of fungi that sustains forests. While most plants engage in mutualistic relationships with fungi, some — like these orchids — have learned to exploit these connections for their own benefit.
In the grand scheme of evolution, mycoheterotrophy is a remarkable adaptation that allows plants to access alternative sources of nutrients. Whether it’s a temporary strategy or the first step toward complete parasitism, the orchids that embrace this lifestyle reveal the diverse and sometimes ruthless strategies that plants use to survive.
“This work is part of a broader effort to unravel the continuum from photosynthesis to complete parasitism. Ultimately, I hope such discoveries will deepen our understanding of the diverse strategies orchids employ to balance different lifestyles, thereby aiding in the preservation of the incredible diversity of these plants in our forests,” concludes Suetsugu.
The study was published in The Plant Journal.
