In budding and grafting the union between stock and scion take place through

In budding and grafting the union between stock and scion take place through Cambium.
In this method, the meristematic tissue of both stock and scion are joined together which is capable of cell division. This tissue is called cambium.
In grafting union between stock and scion produces an undifferentiated mass of cells called callus. A callus is more or less corky secondary tissue developed lay woody plants over a wound. A callus is derived from the cambium.