The processes of graft union formation in tomato

Abstract

Despite the long and widespread use of grafting in tomato cultivation, the structural changes that occur at the graft union during the early stages of the union remain poorly understood. In this study, the structural development of the graft union in tomato plants was examined 3, 5, 8, 11 and 14 days after grafting (DAG) using scanning electron microscopy (SEM) and a paraffin sectioning technique. The paraffin-sectioned images of the transection revealed that parenchymal cells from the graft union divided and proliferated in most combinations, and these cells could be detected at various stages of development. The SEM images of the scion and rootstock longitudinal sections showed that many interconnecting structures appeared at 8 DAG and were followed by a vascular rearrangement that did not connect the scion and rootstock. Vascular bundle bridges appeared at 11 DAG and connected the scion and rootstock. The connection of graft union between rootstock and scion is influenced by the plant growth condition. In our managed environment, period for formation of the connection structure formation between the rootstock and scion was 7-14 days after grafting.