Reversal of Vernalization by High Temperature

Abstract

IN a previous letter¹, evidence was presented showing that ‘Petkus' winter rye vernalized for six weeks and, then exposed for a short period (1-4 days) to a temperature of 35° C showed a retardation of flowering, thus indicating a partial reversal of the vernalized condition. The complete devernalization reported by Efeikin² and Tetjurev³ using winter wheat was not obtained in this experiment with winter rye. After a period of vernalization of twelve weeks, however, high temperature completely failed to cause retardation in flowering. The conclusion was therefore drawn that as the period of low temperature treatment is extended the vernalized condition induced becomes less and less easily reversible and finally is completely stable. This suggestion has been completely substantiated by an experiment carried out in 1947. Winter rye was vernalized for varying periods, using the ‘restricted moisture' method, and at the end of treatment was exposed for three days to a temperature of 35° C. The grain was then sown, both in the field and in pots, and the flowering behaviour assessed by the ‘scoring method' of Gregory and Purvis⁴, which gives a quantitative measure of ‘earliness' of flowering. The results for plants grown in the field are presented in Table 1.