A number of defined desiccation treatments without low temperature exposure were able to induce freezing tolerance in 20 cultivars of winter cereals. A maximal degree of freezing tolerance was induced in epicotyls at 24°C in 24 hours at 40% relative humidity in rye and wheat, 7 days at 54% RH in barley, and 4 days at 70% RH in oats. Freezing tolerance was not correlated to water content of the plants after desiccation treatment but was related to the genetic capacity of the cultivars to frost harden. Levels of freezing tolerance induced by desiccation were similar to those induced by cold acclimation in rye and wheat, but considerably less in barley and oats. This is associated with a more rapid desiccation injury in barley and oats, precluding the completion of the hardening process.
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