In article 2,
Sean Houtman wrote:
Archimedes Plutonium wrote in
:

I have about 5 ulmus thomasii grafts with siberian
elm rootstocks. So I have been watching them
closely for the past years to help me identify
rock elm from other elms. And I wonder how that
works with a graft. Whether the tree thinks it is
RockElm and let the rockelm portion lead in
metabolic signals. Or whether the rootstock metabolism plays roles on
the branches and
leaves.

Just as apples grafted on various rootstocks still grow the same apples,
the top portion of the elm trees will grow according to their genetic code.
Seeds and leaves produced will be 100% U. thomasii. The root portion of the
graft may confer drought or soil-born disease resistance, but won't affect
the top part much.

Dwarfing rootstocks for apples and other tree fruits? ;-)

I think it has something to do with partial incompatibility at the
graft union, but I don't know the details.