Incompetence of stem epidermal cells to dedifferentiate and graft

Abstract

An intact mature epidermis precluded formation of approach grafts of stems of five angiospermous species. When the epidermis was excised, unsclerified cortical tissue exhibited tissue responses resulting in wound closure, including cell dedifferentiation and redifferentiation into callus tissue. Removal of the epidermis from both partners resulted in a graft union. Cortical callus tissue proliferated and coalesced to bind the partners. None of these responses associated with grafting or wound closure occurred in either epidermal or subepidermal tissue in intact partners. Whereas cortical cells adjacent to a cut region reacted in a similar way to those underlying the cut, neighboring epidermal cells were usually unaltered. This developmental quiescence of epidermal cells is a unique characteristic, useful in studies of epidermal differentiation and determination.