Wu, Min-Tze, authorHughes, Harrison G., advisorWallner, Stephen J., committee memberStanwood, Phillip C., committee member2023-01-272023-01-271981https://hdl.handle.net/10217/236130Covers not scanned.This study examined cold hardiness and the occurrence of deep supercooling in stem with an attached bud of 4 cv. of grape and 4 of raspberry. Cryoprotectants were also tested for their influence on cold hardiness of raspberry vegetative bud and stem. Differential thermal analysis (DTA) of 4 cv. of grapes, Vi tis species hybrids, 'Concord', 'Beta', ' Valient', and 'Rougeon' showed that the stem and bud pieces of all cv. deep supercool in winter. They all showed a bud exotherm at approximately -25 to -30°C, and a stem tissue exotherm at approximately -40°C. The temperature at which the bud exotherm occurs may be the killing point of the bud which in turn could lead to the death of the above-ground canes. Evidence of this was the observation of the death of 'Rougeon' buds, bud exotherm observed at approximately -20°C, during the winter of 1980-1981 when the lowest temperature was -2S.6°C. DTA profiles of stem with attached bud samples of the 4 raspberry cv., 'Heritage', Ruhus idaeus L., 'Black Hawk', R. occidentalis L., ' Amethyst', R. neglectus Peck, and 'Darrow', R. allegheniensis Porter, suggest that these do not deep supercool during winter. The mechanism of freezing resistance of these may be tolerance of extracellular freezing. Survival, indicated by sprouting, on January 30, 1981 showed that the LT50 (lethal temperature for at least 50% bud sprouting) was -55°C -50°C, and -45°C for 'Black Hawk', 'Amethyst', and 'Heritage', respectively. This supports the idea that at least these 3 cv. resist freezing by tolerance of extracellular freezing. Therefore minimum temperature may not be the major limiting factor in their northernly distribution. In descending order the observed degree of hardiness was 'Black Hawk', 'Amethyst', and 'Heritage'. Survival tests of 'Heritage' samples treated with cryoprotectants showed no benefit of cryoprotectants for enhancing the resistance of acclimated buds and stem to cold injury. However, there were some implications that cryoprotectants may enhance the resistance of nonacclimated samples to lower temperatures.masters thesesengCopyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright.Fruit-culturePlants -- Effect of cold onText