Environmental and Seasonal Factors Affecting the Frost-induced Stage of Cold Acclimation in Cornus stolonifera Michx

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Abstract
Stem tissues of red-osier dogwood (C. stolonifera Michx.) acclimated from -3.degree. C to -40 or -50.degree. C in 8-10 wk under a short photoperiod (9 h) and controlled temperature conditions. During the summer months plants did not acclimate as well as at other times. The sequence of day/night temperature regimes which induced maximum acclimation was 20/15.degree. C for 5-6 wk; 15/5.degree. C for 2-3 wk; 15/5.degree. C plus 1 h of frost/day for 1 wk. The duration of exposure to each temperature regime influenced the rate and intensity of frost-induced acclimation. Less than 5 wk of warm temperature preconditioning at 20/15.degree. C reduced subsequent frost-induced acclimation. The inductive influence of frost on cold acclimation was additive over 5 days of repeated exposure, but its effects after the first exposure(s) were not immediate, requiring 1-4 days of 15/5.degree. C following the frost treatments for the expression of the frost-induced acclimation to be manifest. There was a 75% increase in rRNA following 3 days of frost exposure and plants in an O2-free atmosphere during frost exposure failed to acclimate. Apparently seasonal acclimation behavior was due to endogenous rhythms rather than developmental stage, and the frost-induced phase of acclimation involves aerobic metabolic processes.