Dear David,
To conclude our exchange of view points on the subject, the following final
information on "panic fruiting".
A) The phenomena of "dying with the tree" and "panic fruiting" could, I
think, be explained in various ways, and so there seems to be an need for
detailed research. Panic fruiting can either be prolific when there's still
enough wood left to facilitate the massive fruiting with lots of or some
extremely big fruitbodies or very poorly with just a few and/or small
fruitbodies when the cellulose resources runs out.
A) In my experience, there are three (to four) types of panic fruiting
macrofungi :
- Obligate (biotrophic) parasitic macrofungi (for the last time) panic fruit
before the tree dies ("death spasmes") or has (almost) succeeded in
compartmentalisation of or closing in the mycelium and eliminating further
growth of hyphae invading living tissues.
- Necrotrophic parasitic macrofungi panic fruit with fewer or much smaller
fruitbodies when they run out of sugars to produce normal sized fertile
fruitbodies from. Perennial bracket fungi develop ever poorer retracting tube
layers "on top of" the layer developed the year before. Sometimes species
such as Ganoderma lipsiense in this phase "recycle" the sterile inside
tissues (trama) to form new layers from, as a result of which very big
fruitbodies become ultra light weight and almost completely hollow.
- Necrotrophic parasitic macrofungi with a dual strategy of colonising living
tissues and/or dead wood (rhizomorphs and spores), such as parasitic
Armillaria species, when forced to produce fruitbodies once the tree dies or
is felled and just a stump remains, panic fruit with massive numbers of big
fruitbodies, because of the need of dispersion of spores over long distance
when the energy source is lost, as rhizomorphs only can infect and colonise
other trees/substrates over short distance.
- Saprotrophic macrofungi panic fruit just before the cellulose to produce
fruitbodies from runs out. Species such as Daedalea quercina often panic
fruit in the form of sterile lumps with a closed in catahymenium once they
have completely brown rotted the heart wood of an oak and for the first time
fruit on the tree.
And then there's the phenomenon of panic fruiting of the infected trees,
which takes place just before, together with, or shortly after the panic
fruiting of parasitic macrofungi and just before the tree dies in a final
attempt ("death spasmes") to spread it's seeds, of which - contrary to a mast
year, when about 70 % of the fruits are fertile - about 70 % is sterile.
And a final question : is Kretzschmaria deusta an exceptional case, because
it starts out from the heart wood as a saprotroph, changes to a parasitic
mode once the mycelium has invaded the cambium and returns to being a
saprotroph once the tree has died ?
And now I shut up too.
Kind regards,
Gerrit
1) In your definition does this kind of fungus kill the living cells in the
process of extracting it nutrients, like a necrotroph, or do they remain
alive, like a biotroph?, or both, like a hemibiotroph?
1) Because trees affected by G. australe (normally) don't show symptoms of
(bark or branch) necrosis or dieback (of parts) of the crown or foliage, like
a biotroph.
2) Are you saying you have evidence that G. adspersum/australe can readily
breach the reaction zone and/or boundary zone of functional xylem and then
colonise that wood in a tree with good vitality?
2) Not evidence on a microscopical level in a living tree (yet), but assuming
G. australe can, because of its (partially sterile) panic fruiting just
before or shortly after the tree dies and not being able to produce
(completely) fertile brackets from dead wood alone.
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