Comparative germination ecology of three short-lived monocarpic Boraginaceae

Germination of seeds and seed bank dynamics of Cynoglossum officinale, Echium vulgare and Anchusa arvensis were studied under natural conditions. The effects of constant and alternating temperature, soil moisture and light were studied in controlled environments. Additionally, for Cynoglossum officinale moist-chilling requirements and the effect of depth of sowing on germination were investigated. The various ways in which Cynoglossum officinale, Echium vulgare and Anchusa arvensis live with mortality-risks related to germination and survival of seeds, are discussed. In the field, Cynoglossum officinale germinates from February till May, Echium vulgare from March till November and Anchusa arvensis from March till July. These three species have a small persistent seed bank. Cynoglossum officinale seeds can persist on the soil surface and on the infructescences, the latter seed bank may last for two years. At 2 and 15 cm depth buried seeds germinated within one year. After three years at 2 cm depth 85% of the Echium vulgare seeds and c. 40% of the Anchusa arvensis seeds had germinated. At 15 cm depth these percentages were c. 25% and c. 5%, respectively. The maximum number of Cynoglossum officinale seeds germinated at 0 10 C 12D/12L and 12% soil moisture. The light response proved to be different for seeds from different populations. A six weeks moist-chilling period can break dormancy. The highest germination percentage was found for a depth of sowing of I cm. Echium vulgare germinated quickly under a wide variety of temperature and soil-moisture conditions. The highest germination percentage was found at 20-30 °C 12D/12L and 6-12% soil moisture. The seeds germinated in darkness just as well as in light. The maximum number of Anchusa arvensis seeds germinated at 15-25°C I2D/I2L and 6% soil moisture. The light response proved to be different for seeds from different populations. A classification of the species could be made, though not strictly, in a species with such characteristics that the mortality risk is reduced in space and time (Cynoglossum officinale) and species with characteristics through which the risk is reduced in space and spread in time (Echium vulgare and Anchusa arvensis).