Acta Univ Latv (2004) 676: 71–77

Graft union formation in elepidote rhododendrons

Abstract

Light microscopy was used to study the graft union formation of splice graft in the elepidote rhododendrons cultivar 'Cunningham's White'. The first visible reaction after grafting was the appearance of a necrotic layer between graft partners consisting of fragmented and compressed cells. Callus was visible six days after grafting and was formed from recent cambial derivatives and phloem rays cells. New cambium and tracheary elements were differentiated from callus cells. Newly differentiated cambium was slightly curved or had an S-shape, and it depended on rootstock and scion tissue matching. When initially the gap between the graft partners remained wide, callus produced more new cambiums: one of them emerged between pre-existing cambium of graft component and an uncommon one – in the pith region. The possible function of this uncommon cambium is discussed.