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 ... :) Rand

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