DEVELOPMENT OF INTERCELLULAR CONNECTIONS BETWEEN OPPOSING CELLS IN A GRAFT UNION

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Abstract
Summary: A morphological and developmental framework is presented for the cellular events leading to graft formation in tomato autografts based on scanning and transmission electron microscopy. Initial adhesion in the pith of grafts is followed by confrontation of new cells generated from the peripheral tissue of stock and scion. Pectinaceous beads on the surfaces of these cells establish a mechanical union between the cell surfaces, forming the functional equivalent of a middle lamella, Plasmodesmata formed de novo at the point of contact between opposing cells link the cell membranes, forming a potential pathway of communication of high specificity. Subsequently, wound vessels differentiate within the ‘callus’ at the graft union, and are connected into the vascular system of stock and scion by wound vessels differentiating from vascular and cortical parenchyma. The significance of these cellular interactions is discussed.