Chimaerae (Graft Hybrids) - specifically Laburnocytisus - what is actually happening?

+ Laburnocytisus Adamii is a Graft Hybrid or Chimaera; produced by grafting Cytisus purpureus (a large bushy shrub with pinkish-purple flowers) onto Laburnum anagyroides (a smallish tree with yellow flowers).

The result is a plant that bears three different kinds of flowers; some that are wholly yellow and look just like the Laburnum, others that are purely pinkish-purple and look just like the Broom, and a third type that are bronze-coloured or mottled - apparently a mixture of the two.

My question (I have googled this, but I can’t find any in-depth info) is: What is actually going on in this plant at various different levels? - do both plants contribute equally to all structures (such as the vascular system etc)?
I presume that the cells of each parent plant remain entirely distinct and that, given sufficiently delicate techniques, tissue could be dissected out and micro-propagated into one or other of the pure parent species?

If anybody else asked this question I would say wait until Mangetout sees it, he’ll have the answer. If you don’t know the answer what chance do we have?

When you ask if the plant can become a pure parent species, do you mean can it reproduce on its own? Do tangelos reproduce on their own? How closely related are the 2 component plants?

Graft chimaerae are a funny one. This particular hybrid arose in a Parisian nursery in 1826 when they used this graft to produce a standard Broom. In one of these grafts (thus, it won’t always occur) the two fused to create this unstable hybrid. This has resulted in the plant reverting to both parent species in addition to producing a ‘hybrid’ flower.

A study conducted almost 100 years ago reports of the “…existence of internal adventitious roots formed in the stock and penetrating to various depths in its tissues. Occasionally these roots even reach the soil and bestow complete independence on the graft.”

http://www.bulbnrose.com/Heredity/graft.htm
An interesting discussion is here–> http://forums.gardenweb.com/forums/load/hybrid/msg0903134115976.html
I like to think of a plant living within a plant that is in turn living in it.

Not a strong answer, but I hope it helps.

No, not really; I’m trying to find out about the actual level of mixing that occurs in the plant; it isn’t the result of crossbreeding, so I think I’m right in saying that there will be no cells that contain genes from both parents, but rather a mixture of cells, some that are pure Laburnum, others that are pure Cytisus.
The question is; what scale (or scales) does this happen at? - is it patchwork or is it a true mixture of different cells? Does any structure in the plant consist only of one species?
Is there any way for a patch of Cytisus cells to migrate to an extremity that consists only of Laburnum cells (or vice versa)?

  • these kind of questions (some of which, I see sarcophilus has answers for).

Yes and no, or rather, Citrus seeds are funny things because the plant that arises from the seed can often come from structures (originally belonging to the parent plant) other than the embryo - so the offspring plant can be an actual clone of the parent. Aside from that, I think Citrus is quite a promiscuous genus and that most interspecies hybrids are fertile - possibly indicating that there is less genetic difference between the species in that genus than perhaps there is between the species of some other genera - but I’m only an armchair botanist/biologist, so take that with a measure of salt.

Laburnum and Cytisus are both in the same tribe:



Phylum Magnoliophyta
      Class Magnoliopsida
       Subclass Rosidae
        Superorder Fabanae
         Order Fabales
          Family Fabaceae
           Subfamily Faboideae
            Tribe Genisteae
              Genus Laburnum
                 Spp
              Genus Cytisus
                 Spp


So… quite close, but probably not close enough to reproduce sexually.

I found this link that I think answers your question:

http://www.habitas.org.uk/gardenflora/taxa.htm

qoute:
GRAFT-CHIMAERAS
Graft-chimaeras (formerly often called ‘graft hybrids’) are a rare
phenomenon arising entirely in cultivation where two species, frequently of
two distinct genera, are grafted together. The chimaera arises as a branch
or shoot from the point of union which contains tissues of both species,
resulting in a combination of both species being expressed in the shoot.
Such shoots have been vegetatively propagated and cultivated and are
available to horticulturists as graft-chimaeras.
The formula for a graft-chimaera uses a + sign to connect the two “parent”
species (not a multiplication sign, to show that they are not sexual
hybrids). An example is: Syringa vulgaris + Syringa x chinensis.
Graft chimaeras can be given cultivar names. The example above has been
named Syringa ‘Correlata’, They cannot be given species names.
(To complicate matters further the parents of this lilac graft-chimaera are
Syringa vulgaris (Common Lilac) and Syringa x chinensis, this second parent
being itself a sexual hybrid of Syringa vulgaris and S. laciniata, known as
the Rouen Lilac!)
If intergeneric, graft-chimaeras can be given their own genus name (which
is a combination of the two constituent generic names) preceded by a +
sign.
Some common examples are:
the Cytisus purpureus + Laburnum anagyroides graft-chimaera which is +
Laburnocytisus ‘Adamii’
the Crataegus monogyna + Mespilus germanica graft has given rise to two
distinct graft-chimaeras, named as separate cultivars:
+Crataegomespilus ‘Dardarii’
+Crataegomespilus ‘Jules d’Asnieres’

unquote