----- Original Message -----
To:
Sent: Tuesday, August 24, 2004 9:25 PM
Subject: Re: [aroid-l] variegated
> At 11:31 PM 8/23/2004, Temmerman wrote:
> >But it still is a bit weird to me that something genetic does not happen
> >all over the plant. Any explanation for that? If not, I guess I'll just
> >have to accept the facts:-)
> >
> >Best,
> >Michael
>
> Hi Michael -
>
> Yes, I know it seems weird until you understand the reasons why. Much has
> been written on this topic and someone on this list already offered a
> reprint of his own article on the subject.
>
> But to summarize:
> Plant chimeras generally result from a mutation in only a portion of the
> plant's tissue. This mutation can occur in an entire layer of tissue
> (Periclinal), or only a portion of a layer (Mericlinal) or only a portion
> of several layers (Sectorial). When it occurs in an entire layer, the
> chimera tends to be more stable. In the other two cases, it is unstable -
> this is due to where a shoot originates on the stem. If it originates
from
> an area that is without the mutation, it grows normally; if it originates
> from an area with mixed mutant and normal tissue, it will also be mixed;
if
> it originates from an area of only mutant tissue, it will contain only
> mutant tissue. leaf or floral variegation is the most obvious type of
> chimera, but others do exist (Harry Lauder's Walking Stick (Corylus
> Avellana 'Contorta') is a mix of slow growing and regular tissue, which is
> responsible for the contorted growth of this famous plant).
>
> An example of the unstable can be seen in:
> http://www.glasshouseworks.com/images/plecvrtv.jpg (Plectranthus
verticillatus)
> Depending upon where you take of cutting from such a plant, you may get
> very different looking plants (variegated a little, a lot, or
> non-variegated). Unless one of these shoots happens to produce a
> Periclinal chimera (it can happen), the variegation will continue to be
> random and unstable.
>
> An example of a stable chimera can be seen in:
> http://www.glasshouseworks.com/images/plecmada.jpg (Plectranthus
> madagascariensis)
> In this common variegate, there is a lack of chlorophyll in the tissue
> layer that grows into the leaf edge. I have a 'sport' of this plant in
> which the mutation 'switched' into a different layer, creating a plant
very
> much like this one:
> http://www.glasshouseworks.com/images4/plect-lothlorien.jpg (Plec. mad.
> 'Lothlorien'), which has a green edge and a pale central area. The stems
> are also pale because they originate from the same tissue as the central
> leaf area. Both of these variegates are relatively stable, but each can
> produce odd shoots from time to time.
>
> I hope this helps a bit - it is a complicated but fascinating topic.
> Regards,
> Seán O.
>
> h o r t u l u s a p t u s - 'a garden suited to its purpose'
> Seán A. O'Hara sean@support.net www.hortulusaptus.com
> 1034A Virginia Street, Berkeley, California 94710-1853, U.S.A.
> (ask me about the worldwide Mediterranean gardening discussion group)
>
>
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