Dandelion variation

George Hammond ghammond at mediaone.net
Sat Dec 16 19:50:32 EST 2000


Janice M. Glime wrote:
> 
>   This discussion on twins brings up a question that has puzzled me for
> some time.  My observations tell me that dandelions in lawns do not
> achieve the height that one finds for dandelions in open fields and
> unmowed areas.  But it also seems that dandelion flowering stalks are
> progressively shorter as the season progresses, at least in lawns.
>   Assuming my observations and memory are correct, does anyone know the
> mechanism behind this progressive and habitat shortening?  I can
> hypothesize several, but have not read anything to support or refute any
> of them:
> 

Hammond:

     Is it correct that a Dandelion is an asexual plant?  Can we
assume that all the Deandelions on the lawn are in fact
"identical genetic clones" for that reason?


> 1.  Competition for light in open areas cause stems to be longer.  That is
> supportable, if in fact the surrounding plants are taller, but my
> observations do not support the latter.
> 2.  Cutting (or herbivory) causes the release of something that inhibits
> stem elongation, making flowering stalks shorter.  (An ethylene response
> could accomplish this, I would think.)
> 3.  There is an actual selection for individuals with shorter flowering
> stalks to survive in lawns.  Those that are taller get cut off and can't
> disperse their seeds.
> 
> Does anyone have any references that support or refute any of these
> hypotheses?  Since the example is familiar to students, it would be a good
> teaching tool, no matter what the explanation.

Hammond:
   
      Then there IS an "environmental variance" among
genetically identical clones?  Is that correct?

> 
> Janice
> ***********************************
>  Janice M. Glime, Professor
>  Department of Biological Sciences
>  Michigan Technological University
>  Houghton, MI 49931-1295
>  jmglime at mtu.edu
>  906-487-2546
>  FAX 906-487-3167
> ***********************************

-- 
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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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