Germination ecology of the endemic Iberian daffodil Narcissus radinganorum (Amaryllidaceae). Dormancy induction by cold stratification or desiccation in late stages of embryo growth

Abstract

Aim of study: We studied the germination ecology of a threatened daffodil in order to develop a protocol to produce plants ex-situ from seeds, a key tool for population reinforcement.Area of study: Experiments were carried out both outdoors and in the laboratory in Albacete (Spain).Material and methods: Embryo length, radicle and shoot emergence were analyzed to determine the level of morphophysiological dormancy (MPD). Effects on germination of cold stratification or desiccation in late stages of embryo growth were also studied.Main results: Mean embryo length in fresh seeds was 1.36 mm, needing to grow up to 2.20 mm to be able to germinate. In the laboratory, embryo growth occurred during warm stratification (28/14, 25/10ºC), and then radicle emerged when temperatures went down (15/4ºC in darkness). Phenology study in outdoors conditions revealed that embryo grew during summer-early autumn, short time after seed dispersal in nature (i.e., May); radicle emerged in autumn. The shoot however did not emerge until late winter-early spring, because it was physiologically dormant and required a cold (5ºC) period of 30 days to break dormancy. Early cold temperatures interrupted the embryo growth and induced dormancy in seeds whose embryo had grown 30% with respect to the initial length. Desiccation in seeds whose embryo had grown 30% did not induce dormancy, but did it when the embryo growth reached 70%.Research highlights: Seeds of Narcissus radinganorum have deep simple epicotyl MPD.Key words: dormancy break; radicle emergence; shoot emergence; epicotyl MPD; phenology; secondary dormancy.

Embryo growth and seed germination of four taxa of Narcissus (section Pseudonarcissi) conserved under non‐recalcitrant seed conditions in germplasm banks

“…Narcissus radinganorum seeds warm stratified under light conditions had higher germination percentages in the dark than in the light. This finding aligns with those reported in an earlier study (Herranz et al, 2015). These seeds were well conserved under non‐recalcitrant seed storage conditions (2.5% moisture; −10°C) and their embryo growth and germination percentages were similar to those seeds conserved at 22°C.…”

“…During warm stratification in the dark, it is difficult to shield the seeds from light while washing them. In contrast, warm stratification in the light and incubation at 15/4°C in the dark achieved 100% radicle emergence in previous studies on N. radinganorum (Herranz et al, 2015).…”

“…Here, the three species whose dried seeds tolerated storage at −10°C ( N. alcaracensis , N. longispathus and N. radinganorum ) differed in terms of their environmental dormancy breaking and germination requirements. They also had various MPD levels (Herranz et al, 2013a, 2013b, 2015). Thus, the ability of a seed to tolerate non‐recalcitrant conservation conditions depends on its maturation drying on the mother plant rather than its MPD level.…”

“…However, shoot emergence requires a cold (5°C) 30‐day period to break dormancy. Its seeds have deep simple epicotyl MPD (Herranz, Copete, Copete, & Ferrandis, 2015).…”

Optimization of Plant Production by Seed Treatment in Two Wild Subspecies of Narcissus pseudonarcissus Rich in Alkaloids

“…An important point to consider when producing these subspecies is that the seeds of N. munozii-garmendiae and N. nevadensis had higher percentage germination rates in darkness compared with light conditions, as also found in other species that belong to the Pseudonarcissus section of Narcissus [ 12 , 13 , 14 , 31 , 32 ]. Photoinhibition is expected to occur mainly in seeds with intermediate seed sizes of 1–27 mg [ 33 ], as found in both N. munozii-garmendiae and N. nevadensis .…”