What happens internally when grafting grapevines?
Would you please provide a description of what happens "internally" when grafting grapevines? What happens to the new part (scion I think it is called) and to the vine? Does the scion grow somehow into the vine, or is it all "one-way" - vine somehow pushing itself into the scion?
Both scion and rootstock grow cells to build a "graft union." Then the new part and old part will become one. All of the new cells come from the vascular cambiums of scion and rootstock. This is why the vascular cambiums (cambia) from scion and rootstock have to line up correctly. Otherwise, the graft will not take.