The Science
Behind Grafting
Branches and leaves obtain water via tube like vessels (xylem) that
run from roots up to the shoot tips. Sugar produced by the leaves
moves down a different type of vessel (phloem) to the roots. For grafts
between two plants to be successful in the long-term, new connections must be generated between these conducting vessels.
The stems of woody plants have a single ring of cells, called the
cambium, which have the potential to produce both water and sugar
conducting vessels. Soon after plants are grafted, the cut
surfaces begin to heal by generating generalized
cells that lock the parts together. Then, if the
cambiums of both stems are aligned, they will
generate new vessels that connect the grafted
pieces so that water and sugar are now able to
move through the graft union.
As with human organ transplants, rejection
Cross-section of a
woody stem.
can occur if the two partners are too unrelated. In
plants, where a classical immune system is not present,
compatibility is more likely. Success is correlated to how closely the
plants are related. No permanent grafts have ever been produced
between plants that are in different families.
In nature, root to root or stem to stem grafting can occur
spontaneously when adjacent roots or stems grow in girth pressing
against each other.