Seed ecology of Synthyris bullii (Plantaginaceae), a rare endemic of the Midwestern USA

Many rare plant species are declining owing to habitat destruction and degradation. Because many populations of rare species suffer low recruitment, a good understanding of seed ecology is crucial for developing effective conservation and management plans. In this study, we examine the effects of shading, seed longevity, and soilless mixes on seed germination for the rare midwestern USA endemic Synthyris bullii (Eaton) A. Heller. Seed germination studies were conducted in a greenhouse environment utilizing seeds from populations collected in Illinois in 2008, 2009, and 2010. In the shading study, both control (66.7% ± 1.3%) and green wrap (63.7% ± 1.3%) had similar and greater percent seed germination than the solid white wove paper (59.5% ± 1.3%). Percent seed germination was similar for seeds collected in 2010 and 2009 (59.5% ± 3.3% and 55.1% ± 4.4%, respectively) in the longevity study, but germination was lower for seeds collected in 2008 (27.1% ± 4.0%) compared with both of the other years. For the soilless mixes study, seeds sown in only one of the three media, Fafard Super-Fine Germinating Mix, emerged (3.5% ± 1.0%). Results from these studies suggest that for S. bullii, (i) seeds may be shade tolerant, (ii) seed viability lessens with age, and (iii) seedlings require a special soilless mix to grow. The information generated by this study can provide guidelines for better seed storage and germination protocols for the conservation of this rare plant species.