Morphophysiological dormancy in seeds of Chamaelirium luteum, a long-lived dioecious lily

Freshly-matured seeds of Chamaelirium luteum have fully differentiated, but small, embryos; mean embryo length was about 1.0 mm. Since embryos in seeds of this species had to grow to 1.3-2.8 mm, depending on the individual seed, before germination was possible, seeds have morphological dormancy. Embryos also are physiologically dormant; thus, the seeds have morphophysiological dormancy (MPD). Cold stratification at 5 degreesC for 12 wk broke physiological dormancy, but embryos in only about 20% of the seeds: grew to greater than or equal to1.3 mm during this treatment. After seeds that had been stratified in darkness at 5 degreesC for 12 wk were transferred to light at a simulated spring temperature (20/10 degreesC = April), embryos in all seeds grew to greater than or equal to1.3 mm within 12 days. Furthermore, seeds receiving 12 wk of stratification in light at 5 degreesC had germinated to 90-100% after 14 days in light at 15/6, 20/10, 25/15, and 30/15 degreesC. Seeds receiving light only during the stratification period at 5 degreesC or only during the 2-wk incubation period at the four temperature regimes germinated to 33-100%, whereas those in continuous darkness during both stratification at 5 degreesC and incubation germinated to only 1-7%. Seeds of C. luteum have nondeep simple MPD. In the field, mature seeds are dispersed in mid- to late autumn, and cold stratification during winter breaks physiological, but not morphological, dormancy of the embryo. However, embryo growth and germination occur rapidly as temperatures begin to increase in early spring.