Are there "Identical Twin" plants?

George Hammond ghammond at mediaone.net
Sun Dec 17 05:23:12 EST 2000


Andrew Dalke wrote:
> 
> >Hammond:  the question then: Is there direct evidence from
> >          crop yield and other agricultural data on parthogenetic
> >          (asexual-clonal) plants, which indicates a significant
> >          VARIANCE in adult size, from which we may conclude
> >          that there is such a thing as an "ADULT GROWTH DEFICIT"
> >          in these plants (in the actual environment), whereby
> >          they are generally always somewhat smaller than some
> >          "theoretical genetic maximum adult size"?
> >            And further, from the Normal Distribution Curve
> >          for the adult size of these (clonal) plants, can
> >          we ESTIMATE the "theoretical genetic size" of the
> >          plant, statistically.... by for instance assuming
> >          that it must be near "2-Standard Deviations" above
> >          the mean clonal size?
> 
> That question isn't very interesting. 

GH:  I'll be the judge of that sir, if you don't mind.


> Because of variations in
> the environment (soil, water, light, pests, etc.) there will
> be variations in size even with with identical genes.

GH:  Thanks for confirming my initial presumption.


>  The
> largest of these sets a minimum value on the size for that
> genotype as a whole.  It is well neigh impossible to estimate
> what the maximum size would be for a species, only set a lower
> bound.
>

GH:  Aren't you neglecting what can be inferred from
     any existing "skewness" in the distribution.
     a normal curve bounded on one side by a 
     theoretical limit is very likely to manifest
     a measurable skew, from which the bound might
     be at least estimated.


 
> In other words, it is tautological that all plants must be
> smaller than their "theoretical genetic maximum adult size."

GH:  Thank you for that confirmation of my presumption.  I
     will certainly quote you on that.



> You will never find a plant larger than that limit.  At best
> all you can do is, as you say, make observations to the
> distribution of sizes and apply some arbitray cutoff in
> the extrapolation to determine what that size might be.

GH:  Yes.... thank you.


> So the answer to your question '[may we] conclude that there
> is such a thing as an "ADULT GROWTH DEFICIT" is "yes" but
> it isn't interesting or useful.


GH:  Whew... someone has actually confirmed my
     argument that there is a "universal growth
     curve deficit".
       Incidentally, this opinion is substantiated
     in HUMANS by the existence of the well known
     and celebrated "Secular Trend" in human generational
     size.  Obviously, it must be simply be a diminishing
     of the "growth curve deficit" with the rising Standard
     of Living.  That, BTW, is in fact the majority scientific
     opinion on the Secular Trend.

> 
> The environment does have a big impact on the size.  For
> example, some plants would do much better in a CO2 rich
> environment compared to what there is now.  Others are
> affected by the timings of the rains.  I'll bet even more
> are limited by being in a 1g gravity field and would grow
> a lot bigger at 1/2 g.  So the environment needed to produce
> the "maximum adult size" might not even be available on
> this planet and any extrapolation you make must necessarily -
> if only implicitly - include that environmental limitation
> in its qualifiers.

GH:  Not a problem.  For my purposes the only environment
     of interest is the "real prevailing natural environment".

> 
> Why is your concern on the adult plant size?  Wouldn't other
> attributes be more important, like ability to produce food
> or to reproduce?  Or drought or pest resistance?  It isn't
> good to be a big plant if you can't survive seasonal droughts.
>


GH:  I am a physicist not a biologist. Actually all of this
     is relevant to the following statement concerning
     HUMAN growth:

"The prevailing theory of [human] growth and nutrition
may be described as the deprivation theory. 
Under this theory, it is assumed that every
individual is born with a given, genetically 
determined, potential growth curve. If the 
individual is healthy and well nourished, he 
will grow along this curve. Per contra, growth
significantly below this curve indicates poor
health and/or malnutrition."

(from: http://www.unu.edu/unupress/unupbooks/80478e/80478E0l.htm)


GH:  Now, this citation takes it for granted that
     there is a "genetically determined growth curve"
     for a human being.  And he recognizes that without
     question many people will fall short of it, 
     mainly due to health insult or malnutrition.
     This is representative of conventional scientific
     opinion in this area.
       What he does not mention, simply because it
     is considered "an uninteresting tautology" as you
     put it, is that NO ONE ever reaches this theoretical
     genetic predetermined growth curve, simply because
     just like the plants you just mentioned, humans
     do not live in a PERFECT WORLD either!
       Moreover, because of this, no one has ever seen
     a "full grown plant", and neither have they ever
     seen a "full grown human being".
       Not only that, it is quite obvious that plants
     may get closer to their theoretical curve than
     humans, simply because they are simpler and less
     complex organisms.


> Hmm.  Thought of a related issue to point out why I don't
> think the question is all that intesting.  Consider viruses.
> Nice, simple reproductive factories.  You can apply your
> same arguments to them to an even higher degree - after
> all, there is a much smaller set of genes needed to make
> the virus and hence less possible variation called by
> environmental effects on gene expression.
> 
> Take HIV as an example virus.  It's an enveloped virus and
> the size of the envelope can vary somewhat.  Again, by
> definition, any HIV virus can be no bigger than the biggest
> possible HIV virus.  Given the distribution of observed sizes
> it's a pretty safe bet that we've never seen the largest HIV
> virus which has ever been produced, much less the biggest
> which could be produced.  Hence, viruses also suffer from
> an "ADULT GROWTH DEFICIT"!  (Because of differences in
> human cells, perhaps a better choice would be a bacteriophage
> virus. I don't know enough about that field to pick a good
> example.)
>

GH:  interestingly, VIRUSES are probably the only living
     organism that have actually REACHED their theoretical
     growth curve.  I say this because you can actually
     COUNT the number of atoms in a T-4 virus for instance,
     and every one of them is perfect right down to the
     last atom.... there IS NO growth curve deficit for
     a Virus.  Remember.... we are talking about NURTURE,
     not NATURE.  A virus is uneffected by NURTURE (i.e.
     every brick is in place regardless of nutrition).


 
> Since your statement can be applied to almost every species
> and for every possible variable characteristic, I can only
> conclude that it is not a very useful concept.

GH:  Whoa Professor!  It is EXACTLY BECAUSE IT IS applicable
     to every living organism (except viruses) that it is of
     the UTMOST USEFULNESS.
       I know you're not prepared for this.... but you brought
     up the matter of "usefulness".
       It turns out that the existence of this "universal growth
     curve deficit" is the "scientific explanation of God".
     Now, DON'T ASK me to go into this.. it is not a proper subject
     for bionet.plants, but if you're interested click on my
     website (URL below) and look for the document labelled "read this
     document first" and it will explain how the growth curve
     deficit causes "God".



> 
> > I'm not advising you to take a graduate degree in theoretical
> > physics either
> 
> Too late.  Already did that.  :)
>

GH:  Hmmm.. wouldn't you know I'd run into one of my own,
     even on a "plant" newsgroup.

     Once again.... thanks for confirming "the obvious"
     for me.  You would be surprised how many people
     I've run into who don't believe it as "obvious", much
     less a "boring tautology"!

     BTW, one last thing.  The "acceleration of gravity"
     was known for 200 years before Einstein redubbed
     it the "Equivalence Principle".  If you didn't
     know that the Equivalence Principle was the foundation
     of General Relativity, I suppose you could call
     Einstein's renaming of gravitational acceleration
     an "uninteresting tautology".
       In the present case, the "growth curve deficit"
     turns out to be the scientific explanation of God,
     and thus another "equivalence principle" in the 
     making. 

     Thanks once again for demonstrating that "only a
     physicist will give you a straight answer to a
     straight question".

 
>                     Andrew
>                     dalke at acm.org




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George Hammond, M.S. Physics
Email:    ghammond at mediaone.net
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