Are there "Identical Twin" plants?
ghammond at mediaone.net
Sat Dec 16 17:05:14 EST 2000
Wayne Parrott wrote:
> George Hammond wrote:
> > GH: You've totally missed the point. I DON'T WANT TO CONTROL ANYTHING.
> > What I want to know is, what is the Standard Deviation of plant
> > growth in the "real environment" when we are talking strictly about
> > a crop of geneetically identical plants?
> > Now, somebody in agriculture must KNOW the answer to this, say
> > for potatoes, or onions or some other asexual crop plant.
> It depends on the variety and on the trait, and it depends if you are talking
> about the SD within a field or between fields. For something like flower color,
> the SD would be close to zero.
GH: Right, I understand that.
> For something like height or yield, it would
> fairly uniform within a field (barring spots which are overly wet/dry, or
> otherwise inappropropriate),
GH: YES, this is what I'm talking about, "gross overall size",
I'm NOT concerned with "specific traits".
There is such a thing as a "growth curve" for
ALL plants and animals and the "plateau" of this
curve represents what we call "maturity", or
However, there is reason to believe that there is such
a thing as a "theoretical growth curve" for any given
genetic species, and that in fact, since a large cloned
plant population has a "terminal growth variance"; that very
few plants EVER achieve this "theoretical growth curve".
Would you agree with this speculation?
but could be quite large between fields, depending
> on how distant they are. Breeders generally call this genotype x environment
> interactions. Genotypes are known which are more stable across environments than
> others. In the end, the SD is difficult to predict without measuring it.
GH: Yes, it is the "between fields" SD that I am talking about.
You apparently agree that such a thing exists and can be
> Keep in mind that plants need not reproduce vegetatively to be genetically
> identical. Hybrids from inbred parents (as in a field of corn) are genetically
> identical. So are inbred plants (as in a field of soybean) and apomictic plants
> (as in dandelions).
GH: yes, this is most interesting. One researcher pointed
out that laboratory mice have been purposely inbred for
thousands of generations, so that within a strain, they
are virtually genetically identical.
My question would immediately be "how much of a growth curve
variance" could these genetically identical mice manifest.
You see; the question here is nothing but the old NATURE-NURTURE
discussion.... with a NEW TWIST.
It is now hypothesized that higher animals, and probably plants,
have something which we could call a "nominal maximum genetic
size", and that in the natural environment, very few IF ANY
individual specimens EVER ACHIEVE IT.
The object then, becomes the task of PROVING THIS CONJECTURE.
> Because of the variability that a given variety of genetically identical plants
> exists, seed companies generally avoid having a central breeding station.
> Instead, they depend on having multiple breeding stations, each one breeding for
> the immediate vecinity.
GH: I see. BTW, on the question of "nominal maximum genetic
size", I think it should be mentioned that "giant vegetables"
are a NATURE (genetic) effect and not a NATURE (environmental)
effect. Seeds for "giant vegetables" have an altered "cell
division gene" that makes the cell-division much more rapid
and that accounts for their giant size.
This is further evidence, that for any GIVEN GENETIC SPECIES
there is such a thing as a "maximum genetic size" of
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George Hammond, M.S. Physics
Email: ghammond at mediaone.net
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