Germination of seeds of Streptanthus bracteatus A. Gray, Bracted Twistflower (Brassicaceae), a Rare Central Texas Endemic

Streptanthus bracteatus A. Gray, Bracted twistflower (Brassicaceae), is a rare central Texas endemic that appears to produce dormant seed; consequentially, acquiring seedlings for field and greenhouse studies is difficult. Factors promoting germination, including light levels and time to germination, were examined in the current studies. Germination of S. bracteatus seeds was significantly greater in the low light treatment than in the high light treatment (non-parametric Wilcoxon rank-sum test, P = 0.0173). Percent germination in the low light was 45% with 30/66 germinating. Germination in high light was 20% with 13/66 germinating. Almost all germinations occurred 5-9 days after seeds were wet. Based on seed mass, all seeds could have germinated: however, 67% of the S. bracteatus seeds were dormant. There may be another factor or combination of factors besides light level that could promote additional seed germination for this species. Published on-line www.phytologia.org Phytologia 96(3): 181-188 (July 1, 2014). ISSN 030319430.