Effect of temperature during burial on dormant and non‐dormant seeds of Lamium amplexicaule L. and ecological implications

Spring‐produced seeds of Lamium amplexicaule L. were dormant at maturity in May and after‐ripened when buried and stored over a range of temperatures, becoming conditionally dormant at low (5, 15/6 and 20/10°C) and non‐dormant at high (25/15, 30/15 and 35/20°C) temperatures. Conditionally dormant seeds germinated to high percentages at 5 and 15/6°C, and non‐dormant seeds germinated to high percentages at 5, 15/6, 20/10, 25/15 and 30/15°C. Seeds that became conditionally dormant at 5°C afterripened completely (i.e. became non‐dormant) after transfer to 30/15°C. Buried seeds that became non‐dormant in a non‐temperature‐controlled glasshouse during summer were still non‐dormant after 12 weeks of storage at 30/15°C, while those stored at 5°C for 12 weeks had entered conditional dormancy. Thus, low temperatures cause reversal of the afterripening that takes place at high temperatures, but not that which takes place both at low and at high temperatures. Low winter temperatures cause dormant autumn‐produced seeds and non‐dormant seeds in the soil seed pool to become conditionally dormant. The ecological consequences of these responses to temperature are discussed in relation to the timing of seed germination in nature.