Seeds of N. hispanicus have deep simple epicotyl morphophysiological dormancy (MPD), with the dormancy formula C(1b)B(root) - C(3)(epicotyl). This is the first study on seeds with simple MPD to show that embryos in advanced stages of growth can re-enter dormancy (secondary dormancy).

Narcissus longispathus(Amaryllidaceae) is a perennial geophyte and a Mediterranean narrowly endemic species. At dispersal time,N. longispathusseeds are dormant and have underdeveloped embryos. This work aimed to determine requirements for dormancy break and germination and to compare dormancy traits with those of the two endemic Iberian congeners. Phenology of embryo growth and germination were studied by regularly exhuming seeds sown in near-natural conditions. Temperature and light requirements for embryo growth, breaking of dormancy and germination were determined by incubating seeds under controlled laboratory conditions. Mean embryo length in fresh seeds was 1.50 mm, and embryos had to grow to 3.80 mm before radicle emergence. Embryos grew to full size and seeds germinated when they were warm stratified for 2 months (optimum 1 month at 20/7°C+1 month at 15/4°C), then cold stratified at 5°C for 2 months, and finally incubated at cool temperatures (15/4°C) for 30 d. However, in seeds only subjected to either warm or cold stratification, the embryos hardly grew and did not germinate. In natural conditions, the embryos elongate in autumn–winter, and in late winter–early spring (March) almost all radicles and seedlings emerged. Velocity of embryo growth and germination percentages increased with seed storage duration. Seeds ofN. longispathushave non-deep complex morphophysiological dormancy (MPD). This is the first report of such a level of MPD inNarcissus. Our data suggest that non-deep complex MPD may have been derived from intermediate complex MPD in the sectionPseudonarcissi.

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 1.01 mm long, and they had to grow to 3.60 mm before radicle emergence. Cold stratification at 5°C for 5 months with light enhanced the mean embryo length to 2.73 mm (SE = 0.13) and seed germination to 20%. However, with higher temperatures (15/4, 20/7, 25/10, 28/14 and 32/18°C) embryo growth was small, with no seeds germinating. Optimal germination was achieved after 4 months of cold stratification at 5°C followed by incubation at 20/7°C 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 25/10°C for 1 month with light was 3.52 mm 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.

The main goal of the study was to assess germination requirements in a threatened daffodil to elaborate a detailed protocol for plant production from seeds, a key tool for conservation. Experiments were carried out both in the laboratory and outdoor conditions. In Pseudonarcissi section, endemic Iberian species of Narcissus studied heretofore have different levels of morphophysiological dormancy (MPD). Embryo length, radicle emergence, and shoot emergence were analyzed to determine the level of MPD. Both interpopulational variability and seed storage duration were also studied. Mean embryo length in fresh seeds was 1.32 mm and the embryo had to grow until it reached at least 2.00 mm to germinate. Embryo growth occurs during warm stratification, after which the radicle emerges when temperatures go down. Seed dormancy was broken in the laboratory at 28/14°C in darkness followed by 15/4°C, but the germination percentage varies depending on the population. In outdoor conditions, seed dispersal occurs in June, the embryo grows during the summer and then the radicle emerges in autumn. The radicle system continues to grow during the winter months, but the shoot does not emerge until the beginning of the spring because it is physiologically dormant and requires a cold period to break dormancy. Early cold temperatures interrupt embryo growth and induce dormancy in seeds with an advanced embryo development. Seeds of N. eugeniae have deep simple epicotyl MPD. In addition, we found that embryo growth and germination were improved by seed storage duration.

Heretofore, no detailed account was available on seed dormancy and germination of a member of the Colchicaceae (Liliales). Thus, the primary aim of this study was to do an in-depth investigation of the temperature requirements for dormancy break and germination in seeds ofMerendera montana(Colchicaceae) at the embryo and whole-seed levels under near-natural temperatures in a non-heated frame shade-house and under controlled conditions in the laboratory. Mean embryo length in fresh seeds wasc. 0.57 mm and embryos had to grow to at least 1.30 mm before radicle emergence. Embryos grew to full size and seeds completed germination (radicles emerged) when they were stratified at 28/14°C for 60 d followed by a cool temperature for 60 d and then incubated at a cool temperature for 30 d. The optimum cool stratification temperature for dormancy-break was 10°C. Thus, after the moist pretreatment at 28/14°C+10°C, radicle emergence was>93% at all incubation temperatures (5, 15/4 and 20/7°C). In its natural habitat,M. montanaseeds are dispersed in June, the embryo elongates to full size in autumn and radicles emerge from early November to early February. Although the shoot does not emerge until March and April, it is not physiologically dormant. The shoot emerged from 80% of the radicle-emerged seeds in 13 d at 20/7°C without a previous cold pretreatment. Seeds ofM. montanahave non-deep complex morphophysiological dormancy, C1b1aB-C1a. This is the first study on seeds with complex MPD to show a delay in shoot emergence following root emergence despite the shoot being physiologically non-dormant.