Answer: There are a number of effects that freezing has on germinating seeds. First, some seeds have a hard seed coat that must be broken down before water can enter and initiate the germination process. Alternating freezing and thawing break down the hard seed coat. Germination itself generally does not occur or is slowed down when temperatures are near freezing. Second, storage of seeds at freezing temperatures can be affected by a number of conditions: type of seed, stage of maturity, prestorage treatment, viability and moisture content when stored, air temperature, humidity and oxygen pressure during storage and degree of infection by fungi and bacteria. Subfreezing temperatures are optimum for the long-term dry storage of many seeds. Temperatures slightly below freezing may be sufficient, but viability has been retained better when seeds were stored at 0 degrees F. Viability of seeds will be reduced if placed in long-term storage at too high moisture content. But seeds can tolerate high moisture content in subfreezing storage better than in cool, above-freezing storage. Seeds that must be kept moist cannot be frozen (beech, walnut, trillium). I hope this answers your question. Please e-mail again if your have further questions about this topic.
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