Differences in the nature of thermodormancy and far‐red dormancy in lettuce seeds

Lettuce seeds cv. Noran germinate at 23°C in light as well as in darkness. However dormancy can be induced either by a long exposure (24 h) to far‐red radiation or by an exposure of 48–72 h to a temperature of 37°C. The difference in response of these two types of dormant seeds to conditions inducing germination indicate that in both types Pfr is inactivated, but that a dark process required for immediate action of Pfr does not proceed at 37°C as it does during far‐red radiation.