Are there "Identical Twin" plants?

George Hammond ghammond at
Sun Dec 17 07:42:04 EST 2000

NOTE: Excuse possible multiple post... newserver technical difficulty
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. 


> 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.
> 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.

> 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. ...<snip>
> the "maximum adult size" might not even be available on this planet

GH:  Not a problem.  For my purposes the only environment
     of interest is the "real prevailing natural environment".
> attributes be more important, like ability to produce food
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."


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.

> 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
> the virus and hence less possible variation called by
> environmental effects on gene expression........<snip>
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".
> > 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 
 Thanks once again for demonstrating that "only a physicist will give
ou a straight answer to a straight question".

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