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Re: Discussion on Origin of Sports...2nd causal factor


Bill and others reading,

If I am the culprit using scientific language and words that are
difficult to understand, I apologize and will try not to do so. I want
to continue my thoughts on the three "explanations"' for sports
mentioned by Ben.. The second one has big words with more than three
syllables but I will translate. According to Ben's Rule of Thumb
mentioned several times in his articles is Chimeral Rearrangement. He
defines it as exchange of cells which exist in layers in the leaf
tissue. He does not go into this subject in detail but appears to
suggest that all chimeral rearrangements are similar or perhaps
identical. One can see how ambiguous the meaning of  words can be when
explanations are not adequate.. In my opinion Ben's chimeral
arrangements are NOT all the same..There is   more than one kind of
phenomena involved here. He stated in one of his articles that he
"calls"  this phenomenon  "chimeral rearrangement", inferring that the
phenomenon is not called by any other name by anyone else. I have not
seen Ben's name given to  this phenomenon used by others scientists.. I
have always seen it described as "tissue shifts" or "tissue exchanges"
on the occasions when the it was necessary to explain how LII (layer
two) on the inside portion of the leaf exchanged position with LI (layer
one) on the outside of the leaf  (epidermis or border of the leaf.) .
This has been described numerous times in articles in the Hosta
literature, including the AHJ. I do not see how Ben has a right to
"name" it differently  from the names already given to it by scientists
who observed and described it first or  have been working in plant
anatomy and cytology for decades now. Other scientists use the term
"replacement"  for the inside to outside tissue shift (LII to LI,  in a
periclinal chimera such as 'Frances Williams' changing to a
mediovariegated sport, for example) and "displacement" for the outside
to inside tissue shift ( LI to LII, for example).

Marcotrigiano explains in his article in HortScience, Vol 32(5),
"Chimeras and Variegation: Patterns of Deceit" that within each apical
layer of the meristem, there are believed to be apical initials, perhaps
three special cells  in each of the two layers, which give rise to cells
within those  layer. Conditions he depicts are not permanent, as
daughter cells of an iniitial may replace other initials and begin to
contribute to a major sector of the tissue layer. Thus, if conditions
allow, a tissue shift may occur. If the shift is uniform for an adequate
period of time, then a new uniform layer of cells grows and develops
into a complete tissue shift or exchange,  resulting in a new and
different chimera . An actual shift of existing tissue does not
occur...tissues do not rearrange themselves. Instead.a new tissue
"grows" into place in a new  position  relative to other tissues. I can
understand as Marcotrigiano has explained it, that this phenomenon can
be a valid reason for causing a different  chimera. Therefore I have no
difficulty with this phenomenon being listed. as a causal factor. But it
did not originate with Ben , nor did whoever controls things  just move
the layers of tissue within the leaf  ( such as  "rearrange the
furniture" within the chimera) , as the term implies.

Thus layer shifts or exchanges are a valid secondary "cause" or
explanation for formation of some sports once a sport  has become
established within a clone of hosta  plants. But chimeral rearrangement
is not a primary cause of sports

If there are any further questions on this phenomenon, I would be
willing to try again if a better explanation is needed. Please note that
I did not use any words of my own  over three syllables.

Jim Hawes

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