Secondary dormancy in light-sensitive lettuce seeds incubated anaerobically or at elevated temperature

Light-sensitive lettuce seeds become secondarily dormant within 8–10 days if initial germination is suppressed by far-red light or incubation at elevated temperature (≥30 °C). When germination is suppressed by temperature, induction of dormancy occurs in both red and far-red irradiated seeds and the process is, therefore, independent of the phytochrome system. Dormancy induction requires oxygen, but reversion of phytochrome from the far-red- to the red-absorbing form appears to take place anaerobically.