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  Re: Chimeric variegation and its pitfalls
From: Rand Nicholson <writserv at nbnet.nb.ca> on 1997.11.23 at 00:02:42(1652)
>Fellow Varoidophiles -
>All this talk of variegated plants and their instability is not a
>new topic on internet forums - it comes up routinely where
>variegated plants are discussed. Among plantspersons I know, there
>are often strong views about what causes variegation in plants,
>usually tending towards the virus factor. I know little about viral
>variegation myself, but I have read a bit on the chimeric type,
>which I find quite interesting. My own observations indicate to me
>that most variegation in plants, especially those that tend to
>revert or 'come and go', is of this type.
>Chimeric variegation is due to a partial mutation IN SOME LAYERS of
>the plants meristem (growing tip) tissue. Even within one layer,
>the mutation may only be towards one side or only effecting a
>percentage of the total tissue layer. This phenomenon takes its
>name from the mythic beast, the Chimera, who was made up of
>different parts of various animals, alluding to the coexistence of
>different tissue in the same plant. Sometimes these mutations are
>visible, as with variegation, or more subtly as with contorted
>plants (one side of the stem grows faster than the other, causing
>the twisting of the growth). Sometimes the mutation is not visible
>in any way, but may still represent a different tissue type only
>detectable by chemical analysis.
>As the tissue grows, only some portions of these layers are
>effected. As tht tip elongates, or new stems arise, the ratio of
>normal to mutated tissue can change and alter sides, etc. This
>causes the random 'splashing' and is the least stable type of
>variegation. Other chimeric variegation can envolve entire selected
>layers of tissue, creating a more regular variegation pattern (e.g.
>pale stems/petioles and central 'flame' variegation on each leaf, as
>both these areas arise from the same meristem layer).
>While some chimeric variegation can be more stable that others, all
>might revert at some point due to various factors (such as those
>discussed - stress, light change, fertilization, etc.) which can
>change the grown rate of the meristem and alter the mix of regular
>and mutant tissue. They can also revert without any apparent
>stimulus due to the happenstance of growth taking place in an area
>free of mutation, usually much more vigorous and therefore likely to
>quickly take over the plant. Careful monitoring of these plants and
>selection of the best variegated parts (along with removal of
>reversions to non-variegated) is the means to sustain the clone.
>Often, new clones can arise from these unstable situations, or more
>stable forms might be selected. It is worth observing.
> Sean A. O'Hara sean.ohara@ucop.edu

Now ...; there's an answer ... :)


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