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.
