Ethylene Effects on Apple Scions1

Abstract

Abstract Dormant apple scions stored in plastic bags with ripening apples at room temperature for 7-14 days show severe swelling and bark splitting due to callus proliferation at the apical end as well as general lenticel hypertrophy (intumescence). This apparent ethylene effect can be duplicated by soaking scions in (2-chloroethyl)phosphonic acid (ethephon) at 1000 ppm for 5 or 40 minutes. One-year-old stems cut into three 20 cm sections show the effect at the apical end of the middle and basal sections, indicating the ethylene-induced injury in related to wounding and that the effect is polar and not necessarily associated with differences in cambial activity that may occur along a stem. Some callus proliferatiomay occur at the basal end of scion pieces if the cut at the basal end is made through a bud. Removal of a ring of bark along the stem of a scion piece does not affect the ethylene-induced injury on the cut apical end but bark swelling may occur at the basal portion of the girdle. Bud excision tends to increase the severity of apical injury to scion pieces.