You know a scientific concept has entered the mainstream when an haute couture fashion collection is designed around it. Iris van Herpen's Roots of Rebirth spring/summer collection "references the intricacy of fungi and the entanglement of life that breathes beneath our feet" and "the miraculous lacery of interconnectedness from the natural 'wood wide web'".
It seems that there are quite a few people out there who want to dress as an interconnected network of fungi and plants, and hooray to that. It is about time that our fungal cousins got the credit they deserve for keeping the world ticking along. After all, fungi are more closely related to animals than the plants they are so often thrown in with in botany departments.
Some 80 to 90 per cent of trees on the planet are hooked into the “wood wide web” where a vast underground network of fungal strands connect the different plants of the forests together. The fungi shunt nutrients and carbohydrates around, benefiting their own growth and reproduction of course, but also influencing the growth, survival and reproduction of their plant partners.
Photosynthesising plants make carbohydrates from C02 and sunlight and trade excess carbs with the fungi for nitrogen, phosphorous and other important minerals that they find it difficult or impossible to absorb through their own roots.
It is not all harmonious exchange below ground. Plants can “hack” the network, taking nutrients but giving nothing in return. Some plants have even come to depend entirely on their ability to parasitise the wood wide web, no longer having any green parts to photosynthesise with and only coming above ground to flower. They have figured out a way to evade the trade.
Fungal network
Even plants which can photosynthesise for themselves have been shown to benefit from the transfer of nutrients when facing hard times. Trees or shrubs in deep shade, where the light is insufficient to maintain themselves, take more than they give from the fungal network. “Mother” trees may contribute more nutrients to their own seedlings via the fungal network than to unrelated seedlings.
These unequal exchanges raise questions about which parts of the network, the plants or the fungi, control who gets what from the below-ground nutrient superhighway. What we see above the surface of the soil as seemingly disconnected individual trees or plants are intimately connected via competitive, parasitic or symbiotic relationships below ground.
The direction of the give and take can depend on local conditions, the individual states of the partners, and a myriad of other ecological relationships which we can only hypothesise about at present.
Plants are not the only hackers. Fungi take advantage of the relationships between plants and their insect pollinators, and hijack both the plant and pollinator to make fungal reproductive spores and transport them instead of pollen.
Spores and pseudoflowers
Spores of the anther smut fungus (Mycobotryum violaceum) are carried by pollinators from flower to flower of white campion where the fungus infects the plant, shutting down the plant’s own ability to reproduce and replacing it with the fungus reproduction system instead. The flowers continue to attract pollinators which unwittingly pick up the anther smut fungus instead of pollen and carry on spreading this sexually transmitted infection.
Just last year, a fungus was found which went a step further – it shuts down the plant's ability to make its own flowers entirely and replaces them with fungal pseudoflowers. The pseudoflowers are entirely fungal in composition but look and possibly smell the same to pollinators as the plant's natural flowers. The fungal pseudoflowerswere discovered on two species of yellow-eyed grass plants (Xyris setigera and Xyris surinamensis) from Guyana.
The ecosystems below our feet are a new scientific frontier requiring new probes, sensors and molecular methods to yield their secrets. With a better understanding of this hidden underworld, we may be able to increase food security, reduce diseases and pests, and improve plant resistance to stresses like drought and salinity.
Next time you look at a mushroom in your fridge, take a minute to think about those interwoven fungal mycelial networks underground that inspire high fashion, control forests and hijack pollinators. Beware our mushroom overlords, they are smarter than they look.
Yvonne Buckley is an ecologist, Irish Research Council laureate and professor of zoology at Trinity College Dublin