GROWING GOURMET - Anto2ni.it

10
THE ROLE OF MUSHROOMS IN NATURE
Figure 11. Intrepid amateur mycologist Richard
Gaines points to a parasitic fungus
Yew
view is rapidly changing as science
progresses. A new parasitic fungus attacking
the Yew tree has been recently discovered by
Montana State University researchers. This
new species is called Taiomyces andreanae
for one notable feature: it produces minute
quantities of the potent anti-carcinogen taxol,
a proven shrinker of breast cancer. (Stone,
1993). If this new fungus can be grown in sufficient
quantities in liquid culture, the potential
value of the genome of parasitic fungi takes on
an entirely new dimension.
Many saprophytic fungi can be weakly
parasitic in their behavior, especially if a host
tree is dying from other causes. These can be
called facultative parasites: saprophytic fungi
activated by favorable conditions to behave
parasitically. Some parasitic fungi continue
to grow long after their host has died. Oyster
mushrooms (Pleurotus ostreatus) are classic
saprophytes, although they are frequently
found on dying cottonwood, oak, poplar,
birch, maple and alder trees. These appear to
be operating parasitically when they are only
exploiting a rapidly evolving ecological
niche.
Many parasitic fungi are microfungi and
are barely visible to the naked eye. In mass,
they cause the formation of cankers and shoot
blights. Often their preeminence in a middleaged
forest is symptomatic of other imbalances
within the ecosystem. Acid rain,
ground water pollution, insect damage, and
loss of protective habitat all are contributing
factors unleashing parasitic fungi. After a tree
dies, from parasitic fungi or other causes,
saprophytic fungi come into play.
Saprophytic Mushrooms:
The Decomposers
Most of the gourmet mushrooms are
saprophytic, wood-decomposing fungi.
These saprophytic fungi are the premier recyclers
on the planet. The filamentous mycelial
network is designed to weave between and
through the cell walls of plants. The enzymes
and acids they secrete degrade large molecular
complexes into simpler compounds. All
ecosystems depend upon fungi's ability to decompose
organic plant matter soon after it is
rendered available. The end result of their activity
is the return of carbon, hydrogen,
nitrogen and minerals back into the ecosystem
in forms usable to plants, insects and
other organisms. As decomposers, they can
be separated into three key groups. Some
mushroom species cross over from one category
to another depending upon prevailing
conditions.
Primary Decomposers: These are the
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