Are there "Identical Twin" plants?

George Hammond ghammond at mediaone.net
Sat Dec 16 20:13:44 EST 2000


Cereoid wrote:
> 
> Sorry but you are mistaken. The "Dandelion" is not an asexually clonally
> propagated species. It reproduces from seeds. Seeds are propagated sexually
> by definition.

GH:  That's what i was asking.. i got the impression Dandelion "seeds"
     were actually "spores"... thanks for the info.


> An asexually propagated species is one propagated from offsets, division or
> tissue culture.

GH:  I'm aware of the definition.

[Hammond]
   Elsewhere you have asked what the BOTTOM LINE of this discussion
is.  well, here it is.  Perhaps you can answer the fundamental question
which is posed below:

> > 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".
      I argue that 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
    "terminal growth".
      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" VARIANCE that I am talking about.
     You apparently agree that such a thing exists and can be
     measured.

> 
> 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:    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.
     That is, proving from existing data, that there is such a
     thing as a "terminal growth deficit" that exists for all
     plants and animals, and naturally we would want to eliminate
     "genetic variation" from the measurements, which is why the
     question has come up explicitly concerning "clonal" plants.


-- 
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George Hammond, M.S. Physics
Email:    ghammond at mediaone.net
Website:  http://people.ne.mediaone.net/ghammond/index.html
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