In article ,
Stewart Robert Hinsley wrote:

Meristems are composed of 3 layers. These can be genetically distinct,
in which case the plant is a mericlinal chimaera. Many variegated
cultivars are mericlinal chimaeras. Sometimes one layer of the meristem
invades and takes over another, leading to reversion of the cultivar.

Thanks. That's one piece of the jigsaw, which either I didn't
know or had forgotten!

But in the case of Physocarpus opulifolius 'Diabolo' reversion there is
the alternative explanation of a mutation knocking out the anthocynanin
synthesis pathway.

Which wouldn't explain how it can revert, unless you then bring
back the previous explanation.

Quite a lot of plants produce multiple types of shoots, which
implies that there is a normal mechanism that does this sort of
thing. Their properties are usually preserved through cuttings,
but not always. If that uses the above mechanism, it indicates
that many plants are normally mericlinal chimaeras! If not, there
is some other mechanism as well.

The truth is rarely pure and never simple ....


Regards,
Nick Maclaren.