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Old 27-06-2003, 07:41 PM
Nina Shishkoff
 
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Default [IBC] one final thing about oak powdery mildew

One of the genera of powdery mildew on oak is the genus Phyllactinia.
The sexual state is a globular structure the size of a pinhead (I
said it was "big", but I meant relative to other powdery mildews) and
has a ring of hairlike spines radiating from it. As the structure
matures, these spines become hygroscopic (moving with changes in
relative humidity), curl down, and push the structure off the surface
of the leaf, so that it is balanced on the tips of the spines,
looking like a tiny robot spider. The top of the structure becomes
gelatinized, so that when a puff of wind knocks the structure off the
leaf, the top adheres to something (for instance, a nearby twig, so
that the thing is now stuck upside down. It spends the winter this
way. In spring a crack forms along the circumference of the
structure, and it opens like a lidded box, releasing the spores just
in time to infect the young unfurling oak buds.


Nina, who, as a mycologist, is never encouraged to tell stories like
this at festive cocktail parties, and becomes more and more of a shy
recluse as the years go by. Still, aren't fungi cool?

PS- if you have trouble visualizing this, go to:

http://www.cals.ncsu.edu/course/pp31...llactinia.html

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