Non-deep simple morphophysiological dormancy in seeds of the weedy facultative winter annual Papaver rhoeas

Embryos in freshly matured seeds of the facultative winter annual Papaver rhoeas are underdeveloped and physiologically dormant; thus, seeds have morphophysiological dormancy (MPD). Seeds lost physiological dormancy during 12 weeks of burial in moist soil at 12 h/12 h daily alternating temperature regimes of 15/5°C, 20/10°C and 25/15°C but not at 1°C. Physiological dormancy was not broken in seeds stored dry at room temperature for 12 weeks. After physiological dormancy was broken, seeds required light for embryo growth (i.e. for loss of morphological dormancy) and consequently for germination. After a 12-week period of burial in soil at 25/15°C, seeds that matured in 1997 germinated to 100% in light at 25/15°C, demonstrating that cold stratification temperatures (≅ 0.5-10°C) are not required for embryo growth. Thus, seeds have non-deep simple MPD. During exposure to low winter temperatures (5/1°C, 1°C), 52% of the seeds with physiologically non-dormant embryos entered conditional dormancy and thus lost the ability to germinate at 25/15°C but not at 15/5°C or 20/10°C. The peak of germination for seeds sown in southern Sweden was in autumn, but some also germinated in spring. A higher percentage of seeds that matured in a relatively warm, dry year (1997) came out of MPD and germinated than did those that matured in a relatively cool, wet year (1998) at the same site.