Mushrooms Appear to Have Electrical 'Conversations' After It Rains

Particularly after rain, the noises of a forest's inhabitants frequently reverberate. Insects buzz and chirp, birds coo and caw, and frogs blip and roar.

However, not all discussions in the forest are audible, and not all of them include animals.

Researchers in Japan have discovered fascinating clues that rain may cause certain fungus to communicate via electrical impulses that are hidden beneath.

At the Kawatabi Field Science Center of Tohoku University in Japan, the researchers concentrated on tiny, tan mushrooms known as bicolored deceivers (Laccaria bicolor), which they discovered growing on the ground of a secondary mixed forest.

The ectomycorrhizal fungus L. bicolor interacts symbiotically with a variety of plants, including many huge trees like oaks and pines. In return for the carbs, it increases their intake of water and nutrients.

According to earlier studies, L. bicolor may even assist certain plants in indirectly feeding on animals by enticing insect cousins known as springtails, maybe killing them with a poison, and then sharing the nitrogen with their host trees.

Unlike certain mycorrhizal fungi, L. bicolor forms underground "sheaths" around the outside of a tree's roots as opposed to penetrating the cell walls of its host plants.

Hyphae, the root-like filaments that support a fungus' development, are used to create these sheaths. Mycorrhizal networks are linked subterranean systems created by the hyphae of mycorrhizal fungus. Such subterranean networks have been likened to a "wood-wide web," in which mycorrhizal fungus and tree roots transmit chemical signals to connect whole woods.

Although mycorrhizal networks do exist, there is little information to say if they are as large and intricate as wood-wide webs. Some scientists claim that many public descriptions of this phenomena exaggerate the situation.

However, this study contributes to a growing corpus of research that explores the specifics of these interactions and provides intriguing insights into how they function.

Previous research has demonstrated that mushrooms alter their electrical potentials ostensibly in reaction to changes in their surroundings, with evidence pointing to the possibility that these signals act as a kind of communication.

For instance, a 2022 research discovered electrical activity patterns in certain fungus that resemble the structure of human speech. The research discovered up to 50 distinct "words," or collections of electrical activity spikes, produced by microbial networks.

Additionally, previous studies have revealed that plants have the ability to transmit subsurface electrical impulses, maybe even independently of mycorrhizal fungus.

The authors of the current study point out that while fungus have previously shown spikes in electric potential, occasionally in reaction to water or other stimuli, the majority of investigations have concentrated on a small variety of fungi cultivated on artificial substrates or gathered from the wild under laboratory settings.

In the latest investigation, scientists affixed electrodes to a collection of six L. bicolor mushrooms they discovered growing alongside a woodland route.

The jolcham oak (Quercus serrata) and the loose-flower hornbeam (Carpinus laxiflora), two possible symbiotic tree species for L. bicolor, were close to where the mushrooms were discovered.

In late September and early October 2021, the researchers observed the electrical potential of the mushrooms for roughly two days. This electrical potential was expressed in millivolts (mV). They write that at first, the research site was bright and dry because there had not been much rain during the preceding twelve days.

On October 1, however, when Typhoon Mindulle dropped 32 millimeters of rain, that situation altered. After about an hour or so of rain, the mushrooms started to respond differently.

Microbial ecologist Yu Fukasawa of Tohoku University explains, "In the beginning, the mushrooms displayed less electrical potential, and we boiled this down to the lack of precipitation." However, once it rained, the electrical potential started to vary, occasionally exceeding above 100 mV.

According to Fukusawa and his colleagues, whose investigation indicates the electrical signal after rainfall exhibited indications of signal transit among mushrooms, this variation was associated with changes in both precipitation and temperature.

According to the researchers, this signal transfer showed directionality and was particularly robust amongst mushrooms that were closer to one another on the forest floor.

Although the new research is far from conclusive, it adds another fascinating piece to the puzzle of how fungus function in the under-appreciated ecosystems of forest floors.

"Our results confirm the need for further studies on fungal electrical potentials under a true ecological context," adds Fukasawa.

The study was published in Fungal Ecology.