Abstract Detail

Ecology

Koontz, Stephanie M. [1], Weekley, Carl W. [1], Menges, Eric S. [1].

Trials and tribulations of waking a seed from its dormancy slumber.

Background/Questions/Methods Seed dormancy is a common trait of plant species associated with fire dominated ecosystems. Numerous studies have demonstrated that smoke, heat and their combination are cues for breaking seed dormancy. Polygala lewtonii (Polygalaceae) is a Florida endemic herb found in longleaf pine/wiregrass ecosystems maintained by frequent fire (2-5 year return interval). Fire kills P. lewtonii individuals but populations rebound quickly. Long-term demographic research has shown moderate year-round seedling recruitment with large pulses following prescribed fire or warm, wet winters suggesting seed dormancy is present in this species. Polygala lewtonii seeds have physiological dormancy with an inhibiting mechanism preventing radicle emergence. Since 2002, we have performed 14 experiments focused on identifying the factor(s) associated with breaking seed dormancy. Variables examined have included sowing depth, medium, season and seed age. We have exposed seeds to smoke, and heated and burned seeds. We have removed elaiosomes, and scarified and soaked seeds in water or smoke water. Here, we review variables tested, sowing methods, and seasonal effects on successful and not so successful germination experiments. Our goal was to identify what worked, what failed, and discuss future directions and variable combinations to determine cues in breaking seed dormancy of P. lewtonii. Results/Conclusions Germination success has been low (mean 8.6%) but has ranged from <1% to 61%. A retrieval experiment yielded 61% germination of seeds sown at 5 cm depth retrieved after 12 months. In two separate experiments, seeds exposed to heat (>60°C) and burned seeds had similar germination (3% and 2% respectively) but were no different than controls (1-3%). Smoke exposure for five minutes in two experiments had higher germination (7% and 17%) than a third experiment soaking seeds in diluted smoke water (1% solution; 2-3% germination). Soaking seeds in water decreased germination (3-6%) compared to controls (9%). Removal of the elaiosome, a fatty appendage, decreased germination, although not always significantly (3-45% vs. 3-38% control). Scarification significantly reduced germination (8% vs. 35% unscarified) and spring/summer settings in a growth chamber doubled germination (14% vs. 6% winter conditions). Experiments with high germination have been associated with smoke or heat, intact seeds, and spring/summer conditions. Current experiments are focused on the effects of seed age and smoke treatments. Ultimately, two main factors associated with physiological dormancy need to be identified: 1) wearing of the seed coat to allow radicle emergence and 2) a cue to stimulate radicle growth.

1 - Archbold Biological Station, 123 Main Drive, Venus, Fl, 33960, United States

Keywords:
dormancy
seed ecology
endemic/rare
germination.

Presentation Type: Oral Paper
Session: 25, Ecology Section: Seed Ecophysiology
Location: 104/Savannah International Trade and Convention Center
Date: Tuesday, August 2nd, 2016
Time: 11:15 AM
Number: 25005
Abstract ID:65
Candidate for Awards:None