Ecophysiology of seed dormancy and the control of germination in early spring-flowering Galanthus nivalis and Narcissus pseudonarcissus (Amaryllidaceae)

摘要

Seed dormancy induction and alleviation in the winter-flowering, moist temperate woodland species Galanthus nivalis and Narcissus pseudonarcissus are complex and poorly understood. Temperature, light and desiccation were investigated to elucidate their role in the germination ecophysiology of these species. The effect of different seasonal temperatures, seasonal durations, temperature fluctuations, the presence of light during different seasons and intermittent drying (during the summer period) over several years' on seed germination was investigated with outdoor and laboratory experiments. Warm summer-like temperatures (20 degrees C) were necessary for germination at subsequent cooler autumn-like temperatures (greatest at 15 degrees C in G.nivalis and 10 degrees C in N.pseudonarcissus). As the warm temperature duration increased, so did germination at subsequent cooler temperatures; further germination occurred in subsequent years' at cooler temperatures following a second, and also third, warm period. Germination was significantly greater in darkness, particularly in G.nivalis. Dormancy increased with seed maturation period in G.nivalis, because seeds extracted from green capsules germinated more readily than those from yellow capsules. Desiccation increased dormancy in an increasing proportion of N.pseudonarcissus seeds the later they were dried in summer'. Seed viability was only slightly reduced by desiccation in N.pseudonarcissus, but was poor and variable in G.nivalis. Shoot formation occurred both at the temperature at which germination was greatest and also if 5 degrees C cooler. In summary, continuous hydration of seeds of both species during warm summer-like temperatures results in the gradual release of seed dormancy; thereafter, darkness and cooler temperatures promote germination. Cold temperatures, increased seed maturity (G.nivalis) and desiccation (N.pseudonarcissus) increase dormancy, and light inhibits germination.(c) 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 177, 246-262.