Abstract
Despite the importance of grafting in horticultural crops such as tomato (Solanum lycopersicum L.), the structural changes that occur during the graft establishment are little understood. Using histological techniques, the present work examines the time course of changes on the anatomical structure of the graft junction in functional tomato homografts and compares it to that of heterografts and non-functional grafts. No apparent differences were detected between homo- and heterografts, showing similar tissue development. At 10 days after grafting, the cell walls of the scion and rootstock in the area of the graft junction were thicker than usual. Undifferentiated cells and new vascular tissue emerged from the pre-existing vasculature. Adventitious roots appeared mainly on the scion, arising from the pre-existing vasculature. At 20 days, more pronounced vascular tissue was visible, along with large areas showing vascular connection. At 210 days, vestiges of the changes undergone in graft development were still visible. Generally, non-functional grafts presented layers of necrotic remains and deposition of cell wall material in the cut edges, impeding the suitable scion-rootstock connection. Our results show that accurate changes in pre-existing vasculature and the cell walls of the adhesion line are crucial to the development of functional grafts.
Highlights
The regenerative properties of plants have been harnessed by growers since ancient times to graft together specimens of different varieties or even species [1]
The aim of the present work was to record the sequence of histological modifications that occur over time in the graft junction of tomato functional homografts, as a model of good scion-rootstock compatibility, to compare it with that of intraspecific heterografts, as a model of moderate compatibility and with that of non-functional grafts
The tissues identified in the stem included a monolayer of epidermal cells, laminar collenchyma, photosynthetic parenchyma, storage parenchyma, primary phloem, vascular meristematic tissue, primary xylem and storage parenchyma
Summary
The regenerative properties of plants have been harnessed by growers since ancient times to graft together specimens of different varieties or even species [1]. Many complex biochemical and structural processes take place during the establishment of a graft, from the response to the initial wound, changes at the edges of the cut, the formation of callus tissue, the differentiation of new vascular tissue, and the connection of the vasculature [2,9,10]. All these processes determine the success of a graft; understanding them, their timing, and where they occur, is key in understanding and promoting graft establishment
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