ABSTRACT
The anatomical and physiological changes which take place within the graft to successfully achieve a union present a fascinating natural process and are well worth investigating. In woody dicotyledonous species the simple non-woody primary growth of emerging seedlings and growing tips of shoots and roots continue developing with age to produce a more complex secondary growth structure. Parenchyma cells are the ‘building blocks’ of a plant tissue known as callus, developed at the site of wounds, including those caused by grafting, and essential to the formation of a graft union. Opinions differ on the effect of root pressure on callus development and subsequent results. The great majority of scientific investigation supports the view that despite close joining of tissues involving interlocking at the point of junction, the original graft components completely retain their genetic integrity and separate identity.
