Intermediate complex morphophysiological dormancy in the endemic Iberian Aconitum napellus subsp. castellanum (Ranunculaceae)

Seeds of Aconitum napellus subsp. castellanum were physiologically dormant at maturity in early autumn, with underdeveloped embryos. Thus they have morphophysiological dormancy (MPD). Embryos in fresh seeds were on average 1.01mm long, and they had to grow to 3.60mm before radicle emergence. Cold stratification at 58C for 5 months with light enhanced the mean embryo length to 2.73mm (SE ¼ 0.13) and seed germination to 20%. However, with higher temperatures (15/4, 20/7, 25/10, 28/14 and 32/188C) embryo growth was small, with no seeds germinating. Optimal germination was achieved after 4 months of cold stratification at 58C followed by incubation at 20/78C for 1 month with light, when germination ranged between 70 and 79%, depending on seed age, locality and year of collection. Cold stratification could be substituted by the application of GA3 solution, since mean embryo length in seeds incubated at 25/108C for 1 month with light was 3.52mm and the germination was 80%. Since cold stratification was the only requirement for the loss of MPD, the longest embryo growth occurred during this treatment, and GA3 promoted MPD loss, we concluded that A. napellus seeds have intermediate complex MPD. Germination was higher in 4-month stored than in freshly matured seeds. A pronounced variability in germinative patterns at inter-annual and inter-population level was recorded.