© 1995 Heron Publishing—Victoria, Canada
Effects of "near-lethal" stress on bud dormancy and stem cold hardiness in red-osier dogwood
A. M. Shirazi (1, 2) and L. H. Fuchigami (1)
1. Department of Horticulture, Agriculture and Life Science Building 4017, Oregon State University, Corvallis, OR 97331-7304,
USA / 2. Department of Botany and Plant Pathology, Oregon State University, Cordley Hall 2082, Corvallis, OR 97331-2902, USA / Received November 25, 1993
Summary
We studied the effects of “near-lethal” (NL, 47 °C for 1 h) heat stress, applied to intact shoots of red-osier dogwood (Cornus sericea L.) during early (October), deep (November) or late (December) dormancy, on bud dormancy release and development of stem
tissue cold hardiness under natural conditions and at a constant temperature of 0 or 23 °C in the dark. The NL heat-stress
treatment overcame bud dormancy when applied during the early and late stages of dormancy. During October and December, all
plants in the 23 °C + dark post-stress environment broke bud within 35 and 12 days, respectively, whereas the corresponding
values for days to bud break in the control plants were more than 150 and 110 days, respectively. Application of NL heat stress
during deep dormancy caused only slightly earlier bud break compared to the control plants. In the 0 °C + dark post-stress
environment, all NL heat-treated plants died within 9 weeks. Under natural post-stress conditions, bud break in plants receiving
NL heat stress during early and deep dormancy occurred at the same time as in control plants, whereas bud break of plants
receiving NL heat stress during late dormancy occurred 55 days earlier than in control plants. Under both natural and 23 °C
+ dark post-stress conditions, cold hardiness of plants receiving NL heat stress during early dormancy was similar to that
of controls. Application of NL heat stress during deep dormancy hastened the rate of deacclimation under the 23 °C + dark
post-stress conditions but had no effect on deacclimation under natural post-stress conditions. Application of NL heat stress
during late dormancy enhanced deacclimation of plants in both the 23 °C + dark and natural post-stress environments.
Keywords:
bud break, growth stages, heat stress, rest, sublethal temperature.
