Role of temperature in regulating timing of germination in soil seed reserves of Lamium purpureum L.

Fresh seeds of Lamium purpureum L. were dormant at maturity, and when buried and exposed to natural seasonal temperature changes they exhibited an annual dormancy/non‐dormancy cycle. During burial in summer, fresh seeds and those that had been buried for 1 year afterripened and thus were non‐dormant by September and October; light was required for germination. During autumn and winter seeds re‐entered dormancy, and during the following summer they became non‐dormant again. Dormant seeds afterripened when buried and stored over a range of temperatures, becoming conditionally dormant at low (5, 15/6°C) and non‐dormant at high (20/10, 25/15, 30/15 and 35/20°C) temperatures. Conditionally dormant seeds germinated to high percentages at 5, 15/6 and 20/10°C, while non‐dormant seeds germinated to high percentages additionally at 25/15, 30/15 and 35/20°C. Low temperatures caused non‐dormant seeds to re‐enter dormancy, while high temperatures caused a sharp decline in germination only at 30/15 and 5°C. The temperature responses of L. purpureum seeds are compared to those of L. amplexicaule L.