Studies on the seed germination and flowering stages of the life cycle of the shale barren endemic Arabis serotina Steele (Brassicaceae)

Arabis serotina Steele is endemic to the shale barrens of Virginia and West Virginia, USA, and long-term seed storage has been proposed as part of the recovery plan for this federally listed endangered species. However, seeds slowly lose viability during storage and must be replaced with new ones, potentially produced by plants held in storage. Thus, it is important to be able to grow plants to reproductive maturity from seeds. The purpose of our research was to determine the environmental conditions required for seed dormancy break and germination, as well as those for bolting and flowering. Seeds were dormant at maturity in autumn, and dormancy break occurred during 12 weeks of cold stratification at 5°C or during burial at natural winter temperatures. After dormancy was broken, seeds germinated over a wide range of temperatures and to higher percentages in light than in darkness. Seeds buried under natural temperatures from October 1990 to March 1991 were nondormant, but those remaining buried until September 1991 were dormant (secondary dormancy). Seeds sown on soil in a nonheated greenhouse in October 1992 germinated in the springs of 1993, 1994, 1995, and 1996, suggesting that the species has the potential to form a persistent soil seed bank. Rosettes required >1235 h of vernalization (i.e., exposure to temperatures from ca. 0°C to 10°C) before subsequently bolting and flowering. However, plants were day neutral with respect to critical photoperiod required for bolting and flowering. Knowledge of the low temperature requirement for seed dormancy break and for vernalization of rosettes for bolting and flowering will facilitate (1) production of new seeds from plants grown from seeds held in long-term storage, and (2) ex situ propagation of the species.