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Contributed Poster

Session: Seed Production, Dispersal, And Predation

PS 19-260 - Physiological dormancy in Pedicularis canadensis, hemiparasite and perennial forb of North America

Monday, August 7, 2023
5:00 PM – 6:30 PM PDT
Location: ESA Exhibit Hall
Abstract:

With climate change threatening plant diversity, seed banks and living collections at botanic gardens will become increasingly important to conservation efforts. Consequently, studying how to overcome dormancies and reliably germinate species of concern will be vital to preserving native species that cannot be stored in seed banks for long periods and propagating plants for reintroduction and ex-situ conservation. Pedicularis canadensis, a perennial forb and hemiparasite native to North America, is threatened in its northern range in Maine. However, P. canadensis’s seeds are difficult to germinate ex-situ. Studying the dormancy of P. canadensis expands gaps in the literature on this species and builds protocols for studying seed dormancy and conservation with hemiparasites.

This research seeks to identify P. candensis’s dormancy type and investigate the germination of this species absent from its hosts. Considering several Pedicularis species have physiological dormancy, the leading hypothesis is that P. canadensis also has physiological dormancy. This research looks to identify dormancy through an elimination process of qualifying conditions of other dormancy types.

In the fall of 2021, P. canadensis seeds were collected from Belchertown, MA, and seed viability was assessed using triphenyl tetrazolium chloride (TTC; redox indicator). Finding the seeds viable, physiological dormancy was analyzed through factorial experiments, first, with cold stratification (0, 2, 4, and 6 weeks) and a period of spring temperatures (25℃/5℃ and 15℃/5℃; light/dark) for up to thirteen weeks, and secondly, with gibberellic acid (1mM and 2mM GA3; plant growth hormone). Considering morpho-physiological dormancy as a potential dormancy type, new P. canadensis seeds were collected in the summer of 2022, TTC testing was completed again, and another factorial experiment monitoring seed and embryo growth was conducted at three different stratifications (30℃/20℃, 18℃, and 15℃/5℃) for ten weeks.

After cold stratification and a period of 25/5℃ or 15/5℃ temperatures, no combination of treatments resulted in any significant germination. Seeds responded to 1mM and 2mM of GA3, having max germination rates of ~92%, and seeds had little to no germination in ethanol or water controls, suggesting that the seeds have signs of physiological dormancy. Pre-germination embryo growth was minimal (7%) over three stratifications for ten weeks and inconsistent between runs suggesting there is not a morphological aspect to the observed dormancy. These findings indicate that P. canadensis exhibit physiological dormancy and begin to clarify understanding of this species’ cycle in the seed bank and dormancy in hemiparasites.