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Old 25-10-2008, 07:50 PM posted to sci.bio.botany
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Default evolutionary purpose of husks on walnut

After dehusking over a thousand black-walnuts, the question is likely
to surface. Why does
a black-walnut or any walnut species have a husk around the nut?
Hazelnuts have a leafy
type of structure over the nut.

Peaches and apricots and plums have fleshy outer covering of their nut
which has caught
the attention of animals to eat that flesh and spread the seed nut,
but not so in the case
of walnut husks.

So has anyone traced a Evolutionary Purpose for the species of nut
bearing trees as
to the purpose of the husk? Is it that the husk or some fleshy part is
required in the
growth of the final nut or hard portion of the nut? Is it that the
energy of growth of the
nut or hardshell is due to the growth of the husk, so that the husk is
integral in the
formation of the hardshell and nut inside? I think that is probably
the answer, since
the seed nut is isolated and nonconnected to the tree except for the
husk.

So, what is the answer? What is the purpose and function of the husk?

Archimedes Plutonium
www.iw.net/~a_plutonium
whole entire Universe is just one big atom
where dots of the electron-dot-cloud are galaxies
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Old 28-10-2008, 02:02 AM posted to sci.bio.botany
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Default evolutionary purpose of husks on walnut

For example, examine the avocado. This fruit evolved symbiotically
with the now-extinct giant sloth. The animal ate the fruit whole and
the fruit offered up its flesh in exchange for having its very heavy
seed propagated. This means that human animals now serve the purpose
of the three toed sloth.

So imagine the walnut being eaten by a now-extinct animal (like
giraffe) which digested the husk as low-grade food and excreted a
viable seed. This theory incidentally explains why domesticated plants
need to be nurseried past the sprouting stage. Seeds excreted into a
steaming pile of nitrogen mulch have a much better chance of growing
It may also explain why walnut shells (and pecan) are loaded with
tannic acid, to acclimatize the seed to an acidic stomach. Compare
that to the fig fruit, which is alkaline and has no hard shell.

-- Gnarlie
http://Gnarlodious.com/Concept
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Old 28-10-2008, 03:26 AM posted to sci.bio.botany
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Default evolutionary purpose of husks on walnut

It would seem my previous post was on the right track. The husks were
eaten by large herbivores that are now extinct. From this page:

http://www.redorbit.com/news/science/261045/ice_age_survivors/

Two unusual survivors aren't animals at all but plants, one of which
is so common that you may have eaten one in the past week or so. The
avocado (Persea Americana) is a South American fruit that has survived
until modem times thanks to the intervention of humans and fanning.
The seed inside the avocado fruit is gigantic and needs to be
swallowed and excreted for it to germinate in the wild. However, no
modern herbivore in South America can swallow such a seed without
choking to death.

This may be the case today, but 10,000 years ago South America had
some of the largest mammalian herbivores ever, including the enormous
ground sloth (Megatherium americanutn), which could grow as tall as
two stories. Coprolites (fossilised poo) reveal that these sloths ate
everything in their region, including the humble avocado.

Here is a classic case of parallel evolution, where two organisms
evolved alongside each other in a symbiotic relationship. The loss of
one almost caused the extinction of the other.

Likewise the osage orange tree (Madum pomtfera), which is found on the
North American plains, also yields gigantic fruits that were once
eaten (and similarly distributed) by the American sloth and mammoth -
some of the only herbivores at the time that could manage the tough-
skinned fruit

Luckily both the avocado and the osage live for a long time, and both
managed to survive just long enough for humans to unwittingly save
them. In the case of the avocado it was farmers cultivating them for
their fruit, while the osage was saved by the reintroduction of the
horse by the conquistadors.
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Old 28-10-2008, 06:17 PM posted to sci.bio.botany
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Default function of husk on black walnut evolutionary purpose of husks onwalnut



Gnarlodious wrote:
For example, examine the avocado. This fruit evolved symbiotically
with the now-extinct giant sloth. The animal ate the fruit whole and
the fruit offered up its flesh in exchange for having its very heavy
seed propagated. This means that human animals now serve the purpose
of the three toed sloth.

So imagine the walnut being eaten by a now-extinct animal (like
giraffe) which digested the husk as low-grade food and excreted a
viable seed. This theory incidentally explains why domesticated plants
need to be nurseried past the sprouting stage. Seeds excreted into a
steaming pile of nitrogen mulch have a much better chance of growing
It may also explain why walnut shells (and pecan) are loaded with
tannic acid, to acclimatize the seed to an acidic stomach. Compare
that to the fig fruit, which is alkaline and has no hard shell.

-- Gnarlie
http://Gnarlodious.com/Concept


Yes, thanks for the suggestion of avocado and of osage orange in
your other post. Before I agree with you on that train of thought, I
need to be assured that the husk is not the "growing part" of the
seed of the black-walnut. I need assurance that the husk is
incidental and not integral to the actual seed growth.

If it is incidental, then the sloth or giraffe would benefit from its
food and the seed benefit in spreading. But if it is integral to
the actual growth of the seed inside, then the evolutionary
pattern requires much more insight.

Compare the husk of hazelnut to that of black-walnut or the
husk of coconut or brazil nut. So I am beginning to think that
a husk, no matter what the size of the husk is somehow
related to the growth of the seed inside and thus has a function
far beyond a animal attractant to spread the seed.

Maybe the husk is the pipeline or channel for which the plant
nurtures the growing nut-seed inside. If I can rule that out, then
I would agree the husk is just incidental and whose function
maybe 100% animal spreading.

Archimedes Plutonium
www.iw.net/~a_plutonium
whole entire Universe is just one big atom
where dots of the electron-dot-cloud are galaxies
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Old 29-10-2008, 12:54 AM posted to sci.bio.botany
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Default function of husk on black walnut evolutionary purpose ofhusks on walnut

I don't believe the husks were necessary as actual nourishment, and I
would say you are turning one component into a big deal. The actual
seed is well protected by multiple layers. Those layers over millions
of years of evolution could have served many purposes, like the hooks
on cockleburs that both served as a propagation vector and prevented
eating. This is similar to the omnivore principle, where
overspecialization eventually led to extinction. The thick-skinned
gymnosperms had many survival strategies, and hanging on to archaic
traits is a valuable asset in adverse conditions. For example, the
previously mentioned page states that osage orange somehow survived
the extinction of woolly mammoths until the horse was imported from
Europe, some 6,000 years without any transport mechanism. Obviously
the plant was able to grow, but probably not with the genetic
distribution needed for homogenity. This may explain why subspecies
arise. Plants typically devote a good part of their metabolic product
to scattering their seeds effectively, and there is apparently a good
reason for it.

-- Gnarlie
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