Tofieldia pusilla seeds and germination

 Tofieldia pusilla produces three carpels (female reproductive structures) with 15-30 ovules per ovary (Flora of the Canadian Arctic Archipelago, FCAA). This could result in 45-90 seeds maximum, but in the Canadian Arctic plants usually only have 6-18 seeds (FCAA). Why so few? This could be either a lack of pollinators (no fertilization) or a lack of resources (too expensive to turn all fertilized ovules into seeds).Seeds are small (0.5-0.6 mm long), smooth, and brown, and contained in fruits that are dry capsules:

Photo: http://nature.ca/aaflora/images/litopuu2.jpg.

Tofieldia seeds do not last long once they are rehydrated. Seeds stored as part of Kew Garden's Millennium Seed Bank Project were rehydrated and then batches were tested every few days for viability (Probert et al. 2009). Within 12 days viability had dropped to 50%, and within 30 days to 0%. This suggests that once seeds become sufficiently moisture to germinate in the spring, they either do so very quickly or not at all. In an arctic or subarctic environment that makes sense (plants that don’t germinate immediately won’t grow large enough to survive by the end of the summer) but it does leave open the question of whether the seeds obtain secondary dormancy and live to try another year.

References:

1. Flora of the Canadian Arctic Archipelago: http://nature.ca/aaflora/data/index.htm

2. Probert, R.J.,  M.I. Davis, and F.R. Hay. 2009. Ecological correlates of ex situ seed longevity: a comparative study on 195 species. Annals of Botany 104: 57-69.