Seed germination requirements of Viburnum lantana were investigated by experiments both in the laboratory and outdoors. Embryo length, radicle emergence and shoot emergence were analysed to determine the level of morphophysiological dormancy (MPD) of seeds. Mean embryo length in fresh seeds was 1.30 mm, and required growth to at least 2.51 mm to germinate. The critical embryo length was 4.1 mm. In the laboratory, the embryo reached 3 mm length after 20 weeks of warm-temperature incubation (20/7 or 25/10°C), which in fact represents a combination of warm + cold stratification. In seeds subjected to cold stratification (1.5 or 5°C) for 24 weeks, embryos hardly grew. Gibberellic acid stimulated embryo growth and germination. In the outdoor phenology test, the embryos grew from 1.30 mm, i.e. fresh seeds sown in September, to 2.98 mm at the end of the following March. In the ‘move-along’ test (laboratory), starting with temperatures of warm stratification [i.e. 25/10°C (4 weeks) → 20/7°C (4 weeks) → 15/4°C (4 weeks) → 5°C (12 weeks) → 15/4°C (4 weeks)], and in the outdoor phenology study on seeds exposed to a similar temperature sequence, radicle emergence percentages reached 73% after 28 and 35 weeks, respectively. V. lantana does not exhibit a delay between root and shoot emergence, dismissing any kind of epicotyl dormancy. Seeds of V. lantana have non-deep simple MPD, a level not detected previously in the genus Viburnum, with the physiological dormancy component overcome by a combination of warm and cold stratification, preferably in that order.
Keywords: Caprifoliaceae, epicotyl dormancy, seed dormancy, Viburnum lantana.
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