it is in the scionwood. Weeping is a plant trait that will be associated with hox genes and/or their regulators.
There are several known traits associated with translocation from the rootstock. This mostly affects fruit. As an example, tomato grafted on jimson weed rootstock translocates hallucination inducing alkaloids into the tomatoes.
I’m using the term “hox genes” very loosely. Genes can be roughly organized into types such as structural genes, protein encoding genes, biochemical genes, etc. Hox genes are the basic structural genes that affect all living organisms. There are equivalents in plants.
Hox genes, a subset of homeobox genes, are a group of related genes that specify regions of the body plan of an embryo along the head-tail axis of animals. Hox proteins encode and specify the characteristics of ‘position’, ensuring that the correct structures form in the correct places of the body.Wikipedia