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VernalizationVernalization is a requirement of some temperate cereal crops and trees for a period of low winter temperature to initiate or accelerate the flowering process. In many plants, flowering can be accelerated or induced by exposure to a long period of near-freezing temperatures. This is a commonly employed reproductive strategy that allows for flowering and seed production in the environmentally favorably period following natural winter. This phenomenon, termed vernalization, has been studied for decades at the physiological level but only recently at the molecular level. The lack of molecular work addressing vernalization is partly due to the fact that in Arabidopsis thaliana, the commonly utilized laboratory strains flower soon after germination, and extended cold treatments do little to further abbreviate the vegetative phase (Koornneef et al., 1998). However, most natural ecotypes of Arabidopsis behave as winter annuals, flowering extremely late in the absence of cold, but very early when exposed to cold for extended periods. Vernalization days (VD) are a measure of cold temperature, similar to growing degree days (GDD) as a measure of warm temperatures. Contrary to popular belief, the best vernalization temperatures are in the 40 F - 50 F range, not at colder temperatures. Vernalization is a biological process and plants have to be biologically active - not frozen - for it to occur.
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