One-year-old kiwifruit [Actinidia deliciosa (A. Chev.) C.F. Liang et R. Ferguson var. deliciosa] vines were grown under 8- and 16-hour photoperiods to study the influence of photoperiod on cold acclimation and determine the potential level of hardiness that young vines attain. Vines were acclimated by reducing growth chamber temperature at 2-week intervals, beginning at 31/20C (16 hours/8 hours) and ending with 15/5C after 8 weeks. Vines receiving an 8-hour photoperiod were more cold hardy than vines receiving a 16-hour photoperiod after 4 weeks of acclimation as determined by electrolyte leakage from stem tissues. Moreover, vines receiving an 8-hour photoperiod survived freezing at – 9C at the end of the 8-week acclimation period, whereas those receiving a 16-hour photoperiod were killed at – 6C. Vine survival and electrolyte leakage of sterns were highly correlated (r = – 0.79 to – 0.90).
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