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Induction of thermodormancy in Avena sativa seeds

Abstract Freshly harvested oat (Avena sativa L.) seeds are considered to be dormant because they are unable to germinate at relatively high temperatures (above 20°–25°C). This primary dormancy results partly from the structures surrounding or adjacent to the embryo (pericarp, testa and endosperm) and partly lies in the embryo itself. Incubation of imbibed dormant seeds at 30°C induces a thermodormancy which is expressed as germination in a narrower temperature range. Induction of thermodormancy is apparent after 3–8 hours at 30°C, is optimal after about 1–2 days at this temperature, but diminishes with longer treatment times. Although whole grains become more dormant as a result of such treatment, the embryos themselves become less dormant, therefore the tissues covering or adjacent to the embryos must have become more inhibiting or the embryos have become more sensitive to their inhibitory action. The germination and sensitivity to ABA or oxygen of embryos isolated from such seeds are no longer so dependent on temperature. The effect of high temperature on primary dormancy and induction of thermodormancy is discussed with reference to sensitivity to ABA and temperature.