Are there "Identical Twin" plants?

Lee Hadden hadden at wingate.edu
Sat Dec 16 10:52:38 EST 2000


I'll give this a shot since I claim to be a plant biologist [and ought
to be able to answer it with some accuracy : )
My responses are  within the body of the letter:

George Hammond wrote:

> Dear Bionet:
>    I am a Physicist not a Biologist.  I have a simple
> question about asexual plants.
>
>    At the following URL:
>
> http://www.uwc.ca/pearson/biology/asex/asex.htm
>
> We find the following statements:
>
> "Asexual reproduction does not allow genetic variation,
> but guarantees reproduction (no dependence on others).
> It rapidly increases numbers of an organism and keeps
> its desired combination of traits."
>
> "Economically speaking, it is very beneficial to reproduce
> plants asexually. It guarantees a "perfect" product every
> time because once the desired combination of genes is found,
> there is no need to risk losing it through sexual reproduction."
>
> [Hammond]
>   Now, a Potato, some forms of Garlic, Gladiolas, Strawberries,
> etc. are examples of asexually reproducing plants described above.
>   What I want to know is this for instance:  Is it possible
> to actually plant 100 acres of Potatoes.. producing many
> metric-tons of potatoes, and actually have each and every one
> of these Potatoes ABSOLUTELY GENETICALLY IDENTICAL:  Yes, barring
> mutation.
>
> 1.  Is this "theoretically" possible?

> Not just theoretically , but practically,  when the seed potatoes
> are identical or are from the same hybrid / cultivar [or same "eyes"
> from the same  potato and its descendents].

> 2.  Has anyone ever done it?

> I don't plant 100 acres but the potato patch in my garden is exactly
> what you are  asking about, just on a smaller scale.   I thinks that
> potato fields would be far larger that 100 acres.

> As far as research is concerned, this would be the equivalent
> of "Identical Twins" testing in Psychology... only now we
> would have a database consisting of MILLIONS of Identical Twin
> Potatoes.  Is this correct?       YES- genetically identical, but
> since no two objects can occupy the same place at the same time,
> their environment can never be "absolutely" identical.  The subtle
> and no-so-subtle influence of those environmental differences would
> produce slight to great variations in growth characteristics.
>
>   The reason I ask, is that the question has come up as to
> whether you can actually PROVE that there is such a thing as
> a "growth curve variation" which is ABSOLUTELY INDEPENDENT
> of "genetics".  It seems to me, simply measuring the yearly
> crop yield variation in such a planting of "Identical Twin
> Potatoes" would prove that such a thing exists.  Has this
> already been proven.  Is it a commonly known biological
> fact of Plant Biology?

Growth curve implies life;  living things are genetically based; to
talk of an organism absolutely independent of its genetics sounds
inherently self contradictory.

Too many absolutes here!  "absolutely" and "millions"  set one up for
the inevitable exception[s] and environmentally -induced variations in
growth inherent in living systems.  [Perhaps as realistic as "ignoring
friction" in my physics lab computations in years gone by???]
But to try to respond----      If each and every plant in our 100 acre
field experienced the [absolutely] identical environmental factors and
conditions, then there should be no variation in plant growth
[productivity, biomass]. Not being a geneticist, but willing to hazard
a guess nonetheless, it seems to me that  since living systems reflect
their genetic constitution, identical or varied, PROVING that anything
regarding living systems is ABSOLUTELY INDEPENDENT OF GENETICS would
not be possible.   The genetic potential of an organism may or may not
be realized if, for instance in the potato example, one plant shades
its neighbor more than it is shaded, or insects chow down on one plant
more than another, one plant has a rock under it and its roots are
impeded, another grows near the favorite defecation site of a mouse
family, or competition for nutrients which would be at best, slightly
varied in different parts of the field, etc., etc...................

Even among all these millions of potato twins, the shape, and size of
the new potatoes, damage by herbivores, etc., will not be absolutely
identical.   Genes determine what might be [and certainly what cannot
be], and the environmental [even micro environmental] factors affect
the fulfillment and expression of that genetic potential.  Without
genes you don't have an organism since organisms are genetically
based.  Organisms have to live in one place or another and even small
differences in their environments can affect gene expression and
resultant growth and performance.

Dr. E. Lee Hadden
Professor of Biology
Department of Biology
Wingate University
Wingate, NC   28174

hadden at wingate.edu
704.233.8238



>
> Thanks in advance,
> George Hammond, M.S. Physics/Psychology
> --
> BE SURE TO VISIT MY WEBSITE, BELOW:
> -----------------------------------------------------------
> George Hammond, M.S. Physics
> Email:    ghammond at mediaone.net
> Website:  http://people.ne.mediaone.net/ghammond/index.html
> -----------------------------------------------------------
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