Myco
hizae in the Ecosystem
NATIONAL CENTER FOR CASE STUDY TEACHING IN SCIENCE
NATIONAL CENTER FOR CASE STUDY TEACHING IN SCIENCENATIONAL CENTER FOR CASE STUDY TEACHING IN SCIENCE
Revolt of the Fungus People:Revolt of the Fungus People:
Myco
hizae in the EcosystemMyco
hizae in the Ecosystem
y
Clyde Freeman He
eid
Department of Biological Sciences
University at Buf alo, State University of New York
Take One
“I’ve got it.”
“What?”
“T e theme for your sci-f f ick. Your requirement for your f lm class.”
“It had better be good. My whole grade depends on it. Just don’t give me a bunch of weird stuf . T is is supposed to be realistic.”
“It’ll be great, I’m telling ya. Suppose it’s like Avatar, except it’s here on Earth.”
“Avatar? T e movie? What do you mean?”
“Remember that part where Earthlings destroy the HomeTree and then try to do the same to the Tree of Souls, really ticking of
the mother goddess, Eywa? And she sends out the word. T en the whole Pandora planet’s creatures take revenge.”
“So? Are you telling me you want to redo the movie? Get serious.”
“No, listen, it would be awesome; it would be here on Earth. Something like that is probably happening right now.”
“You’ve lost it.”
“No really. I mean, I just read that right here on Earth there’s an underground web connecting the plants and they communi-
cate to fend of predators. Like it’s fungus or something that connects everything. And the plants send chemical messages to one
another, telling the predators to back of or they’ll kill them.”
“T ink of it. It could be realistic with scientists discovering that a slow creepy takeover of the planet is happening under our
feet. Or a fantasy like Oz with trees throwing apples at the Scarecrow and Dorothy ... or like Lord of the Rings where
TreeBeard led the Ents army on an attack on Saruman’s fortress at Isengard, or like a ho
or f lm, with giant celery plants
stalking the night.”
“Stop. Stop. T at’s awful. Where do you get stuf like this? But the idea doesn’t totally suck, if it’s really true.”
“I’m telling you, this is real stuf . T e prof will eat it up.”
•
Part I – Networking
Almost all land plants are connected together by an underground network of symbiotic fungi called myco
hizae. T ere
are thousands of dif erent species of these symbiotic soil fungi which entangle plants’ roots living between and within
their cells. A spider web of tiny fragile fungal cells tunnel through the soil linking all of the plants together. T e fungi
draw ca
ohydrates from the plants and the plants in turn collect nutrients and water from the fungi. As much as 80% of
a plant’s nitrogen and phosphorous plus minerals like copper, iron, potassium, zinc, calcium and sulfur can come from
“Revolt of the Fungus People” by Clyde Freeman He
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NATIONAL CENTER FOR CASE STUDY TEACHING IN SCIENCE
the myco
hizae. But can plants share their resources
with each other via the fungal grid?
Biologists have long suspected so. Scientists in Switzer-
land have now traced ca
on molecules slowly moving by
cytoplasmic fow from tree to tree by this underground
fungus pipeline (Klein et al., XXXXXXXXXXIt has been estimat-
ed that up to 4% of the forests’ ca
ohydrate production
from photosynthesis passes along this superhighway.
Klein and his coworkers started their experiments by
lowing “standardized” CO2 through a system of thin
perforated tubes interwoven among the needles of Nor-
way pine trees. Tey followed ca
on 13 atoms (using
the technique of stable isotope labeling) as they were
picked up during photosynthesis and passed from CO2
into sugar and other organic molecules. T e labelled
CO2 was not detected in the air of neighboring trees or
on the ground so the scientists felt secure that only the
test trees were receiving the labels. Tis meant that when
the ca
on 13 label was detected in neighboring trees,
the scientists could safely conclude that the molecules
had been transported between plants by way of the soil
network and not by way of the air. Interestingly, some of
these adjoining trees participating in the exchange were
European Birch and Larch trees, completely dif erent
species than the pine (Figure 1). Te researchers became
satisfed that the fungus was indeed the pipeline when
they found that labelled organic molecules were detected
in the mushrooms of fungi that were linked to the Nor-
way Pine. Tese are called ectomyco
hizal myco
hizae
ecause they live on the surface of roots and between the
oot cells. Tey did not fnd labelled ca
on in mush-
ooms that were not part of the myco
hizae network
ut were soil fungi that
eak down dead organisms (i.e.,
saprotrophic fungi).
In another important related study, researchers in British
Columbia studied the fungal and Douglas fr tree interac-
tions in a 30 × 30 meter plot of ground (Beiler et al.,
2010). Tey collected samples of two myco
hizal spe-
cies connecting the various trees. Tey determined that
all of the 67 trees in the plot and 64 trees outside were
interconnected in a complex network (Figure 2). Trees of
all ages were involved but the oldest trees had the most
connections; one 94 year old “hub tree” connected to 47
other trees by way of 8 myco
hizal individuals of one
fungus species and 3 of the other. In principle chemical
products could be interchanged throughout the system.
Figure 1. Te interconnections of myco
hizae and trees in a for-
est. Myco
hizae are involved but other soil fungi are not. Organic
molecules can be exchanged between diferent species of trees via this
oute. Ca
on and nutrient fow tends to move from trees which are
in the sun to trees that are shaded and from older trees to seedlings.
From: Van der Heijden, M XXXXXXXXXXUnderground networking. Science
352: 290–1. Reprinted with permission from AAAS.
Figure 2. Diagram of a 30 m × 30 m plot in a Douglas fr tree forest
of British Columbia. Each green circle is a tree and the various lines
depict the connections between individual trees by the myco
hizae.
Te tree at the lower right of the diagram (indicated by an a
ow) is
connected with 47 others in the plot. From: Beiler et al., 2010, “Archi-
tecture of the wood-wide web,” New Phytologist 185(2): 543–53, used
with permission of John Wiley & Sons.
“Revolt of the Fungus People” by Clyde Freeman He
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NATIONAL CENTER FOR CASE STUDY TEACHING IN SCIENCE
Questions
1. What propels the movement of chemicals like ca
ohydrate through the thin hyphal cells of the fungus?
2. How did this sharing of resources evolve? What possible advantage could there be to organisms sharing resources?
3. Can you provide a reasonable sequence of steps for a fungus to establish a symbiotic relationship with plants?
4. Tere are some plants (e.g., Indian pipe, orchids) that do not have chlorophyll yet they are connected to the
myco
hizal web. What would you suspect their relationship to be?
5. What do you anticipate the consequences are to the plants when the earth is plowed up or strip mined?
6. What impact might a logging practice of cutting the largest trees in the forest have on the health of the ecosystem?
“Revolt of the Fungus People” by Clyde Freeman He
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NATIONAL CENTER FOR CASE STUDY TEACHING IN SCIENCE
Tree Talk
“No BS. Te whole earth is crawling with these fungi. Tey’re like a Facebook network connecting friends everywhere.”
“Okay, okay, you’ve convinced me that trees share food with fungi. I’ll never eat a Portobello sandwich again without thinking
I’m munching on the whole forest. But what’s this news you were giving me about trees warning each other about parasites
and predators and impending doom?”
“It’s real. Plants talk to each other. Tey send gas messages through the air. It’s kinda like that kid book Buried Onions where
Gary Soto talks about vapors coming from a giant onion buried under Fresno. ‘Te remarkable bulb of sadness.’ ”
“What the devil are you talking about? Do you mean plants are spewing out hallucinogens? Droppin’ acid?”
“Be serious. When plants are attacked by insects, their leaves give of vapors or fumes that let their neighbors know there’s
trouble and the neighbors start making chemical defenses that will ward of the attack.”
“But wha...?”
“Hang on. Tere’s more. Even better. Plants can send these warnings by the underground network. Like tiny TV cables. Fungi
with connections everywhere.”
“So what am I supposed to do with all of this botany? I’m shooting a f lm and I’ve got to put together a trailer this week.”
“Like I told you. Tese plants talk to each other and let’s say they want to take over the world. Humans are making a mess of
everything. We’ve screwed up the air. We’ve screwed up the water. We’ve screwed up everything we touch—ruining the land
with cities and parking lots—rippin’ up the network. Killing all of the animals in the forest and land. Overf shing and mur-
dering whales. Te whole planet is in deep doodoo. Extinction is everywhere. Te world is a mess and the plants know it. So
do the animals. It’s revenge time. Tat’s when the fungi rebel. Tat’s your theme in a nutshell. Now go and make your trailer.
Remember the remarkable bulb of sadness.”
•
Part II – Ai
orne Alert
Plants aren’t helpless; and yet when you look at them just standing there with limbs outstretched to the world, they
seem to be welcoming all insults. Cows, ze
as, snails, grasshoppers, and ra
its graze upon them. Deer, giraf es, koa-
las, and goats
owse on them. Bees, hummingbirds, moths, and butterfies suck upon them. Elephants rip them from
their moorings and gorge upon them and even cute pandas munch on their shoots. It is the same under water. Hordes
of minute algae are being go
led up