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- Author or Editor: Patrick Pierquet x
The technique of differential thermal analysis was used to examine midwinter hardiness of bud and stem tissues of Vitis riparia. Low temperature freezing points (exotherms) were found to occur in both stem and deacclimated bud tissues. Exotherms were not exhibited by fully acclimated buds. The temperature at which the stem tissue exotherm occurred was independent of cooling rate and duration of a thawing pretreatment of 6 to 48 hours. The initiation temperature of the bud exotherms varied with cooling rate and duration of a thawing pretreatment of 6 to 48 hours; an increase in either caused the bud exotherm to occur at a higher temperature than that of the control. It is postulated that deep supercooling of the intracellular water in stem and bud tissues is the characteristic which limits the northern distribution of V. riparia.