Studies in Vernalisation of Cereals: XIV. The Thermal Reactions in Vernalisation

Vernalisation of Petkus winter rye can be reversed by high temperature.Such devernalisation was prevented or diminished by a periodat the ‘neutral’ temperature (about 13° C) immediatelyafter vernalisation, by weak light, or by restricting the growthof the seedlings by limiting the water-supply. Before vernalisationwas completed, each additional week at low temperature approximatelyhalved the percentage devernalisation possible. Prolonging theheat treatment after vernalisation led to a secondary accelerationof flowering. By subjecting intact grain and excised embryosto various alternations of low and high temperature, data wereobtained from which the Q₁₀ of the devernalising process wasestimated to be approximately 4, and independent of the presenceof the endosperm. Exposure to high temperature before vernalisation(pre-devernalisation) reduced the effect of the cold treatmenton intact grain and, to a much less extent, on excised embryos,but did not prevent completion of the process accelerating floweringif low-temperature treatment was prolonged.