Epicotyl morphophysiological dormancy in seeds of Lilium polyphyllum (Liliaceae)

Abstract

Dormancy-breaking and seed germination studies in genus Lilium reveal that the majority of Lilium spp. studied have an underdeveloped embryo at maturity, which grows inside the seed before the radicle emerges. Additionally, the embryo, radicle or cotyledon has a physiological component of dormancy; thus, Lilium seeds have morphophysiological dormancy (MPD). A previous study suggested that seeds of Lilium polyphyllum have MPD but the study did not investigate the development of the embryo, which is one of the main criteria to determine MPD in seeds. To test this hypothesis, we investigated embryo growth and emergence of radicles and epicotyls in seeds over a range of temperatures. At maturity, seeds had underdeveloped embryos which developed fully at warm temperature within 6 weeks. Immediately after embryo growth, radicles also emerged at warm temperatures. However, epicotyls failed to emerge soon after radicle emergence. Epicotyls emerged from >90% seeds with an emerged radicle only after they were subjected to 2 weeks of cold moist stratification. The overall temperature requirements for dormancy-breaking and seed germination indicate a non-deep simple epicotyl MPD in L. polyphyllum.

Overcoming root dormancy and identifying the storage behaviour of Lilium polyphyllum seeds

“…After all treatments, seeds were sown at a depth of approximately 1cm in styrofoam trays containing a mixture of soil, sand, and litter in 1:1:1 proportion and placed in a non-temperature-controlled greenhouse (hereafter referred to as the 'greenhouse') at Srinagar Garhwal (550 m a.s.l.). The day and night temperatures in the greenhouse were about 28 and 12 °C, respectively, (average of 20°C); 20°C had previously been shown to be a favourable temperature for root emergence (Dhyani et al 2013). The soil was moistened, as required, with running tap water to keep the surface moist.…”

“…In contrast, in the laboratory the root emerged from >90% of the seeds after 8 weeks of incubation in 12/12h light/dark cycle at 20°C. Then, after a short period (14 days) of cold (0-4°C) moist treatment the shoot emerged from >80% of the seeds moved from 0-4 to 20°C (Dhyani et al 2013). Thus, a high percentage of the seeds give rise to a healthy seedling in the laboratory under controlled temperature conditions, i.e.…”

“…The embryo also has physiological dormancy (PD). That is, the seeds have morphophysiological dormancy (MPD) (Dhyani et al 2013). Seeds are dispersed in autumn (October, <15°C), and it takes about 34 weeks for the cotyledonary petiole/sheath (hereafter root) to emerge.…”

“…Thus L. polyphyllum seeds take approximately 18 months from seed dispersal to complete germination (leaf emergence) in Himalayan temperate coniferous forest of Garhwal, India (Dhyani et al 2010). That is, seeds have epicotyl MPD (Dhyani et al 2013).…”

Callus-Mediated Organogenesis in <i>Lilium polyphyllum</i> D. Don ex Royle:A Critically Endangered Astavarga Plant

“…The situation is further aggravated by the epicotyls-morphophysiological seed dormancy in L. polyphyllum 11 . Due to dwindling population of the species in the wild, it has resulted into the threatened status in the Red Data Book of Indian Plants 12 and subsequently as critically endangered by IUCN 1 .…”