Acta Univ Latv (2007) 723: 155–162

Simultaneous graft union and adventitious root formation during vegetative propagation in elepidote rhododendrons

Abstract

Light microscopy was used to carry out a detailed study of cutting graft (grafting on unrooted cuttings) in simultaneous graft union and adventitious root formation using elepidote rhododendron cultivars ‘Cunningham’s White’ as rootstock and ‘Catawbiense Grandiflorum’ as scion. The first visible reaction was the appearance of a necrotic layer in scion, rootstock and the base of rootstock, observed on day 2 after experimental initiation. The next observable reaction was callus formation from cells in the cambial region. The wound vascular cambium was first recognizable on day 21, and the cambium bridge (a continued strand of wound vascular cambium in callus tissue) between rootstock and scion on day 30. Simultaneously, root initial formation from phloem ray was observed on day 30. Root initials differentiated into root primordias and they continued to develop till emergence at the surface of the rootstock base. Cutting graft is a quick propagation technique that reduces substantially time from unrooted cutting graft to field plant. It may be useful as a method of rooting of varieties showing poor rooting potential.