Shulman, Y., Institute of Horticulture, Agricultural Research Organization, The Volcani Center, P.O.B. 6, Bet Dagan, Israel

Shedding of the upper parts of unlignified grapevine (Vitis vinifera L.) canes is frequent during autumn. Stress conditions during the growing-season lead to similar shedding of shoot tips. The separation process occurs above a node in the boundary area between the distal part of the diaphragm and the pith. Ethephon (2-chloroethyl-phosphonic acid) sprays, at 750 or 1500 mg l-1, induced separation of the shoot tips of 'Perlette' and 'Queen of the Vineyards'. Ethylene (C2H4) 200 vpm and ethephon at 10, 100 and 1000 mg l-1 enhanced separation in shoot explants, whereas 2,4,5-TP (2,4,5-trichlorophenoxy-propionic acid) at concentrations above 1 mg l-1 arrested it. This phenomenon may be regarded as a shoot abscission process which may represent adaptation of self-pruning of the grapevine. © 1982.