Breaking Seed Dormancy in Three Poaceae Species

Seed dormancy is a major impediment to germination testing in seed testing laboratories. Dormant seeds are alive but do not germinate under conditions favorable for germination of non-dormant seeds of the same species. Dormancy in many pant species can be broken using a single ·treatment or a combination of treatments. Treatments commonly used are light or dark, various temperature regimes, prolonged exposure to cold treatments (pre-chilling), and the use of growth hormones or other chemicals. Three Poaceae species, winter wheat (Triticum aestiivum), prairie drop seed V (Sporobolus heterolepis), and prairie cordgrass (Spartina pectinata), were the subject of this research. Winter wheat seed dormancy can be a problem because of the short turn around from harvest to planting in the upper Midwest. New crop wheat seeds need to be planted and exposed to cold temperatures (5°C) for five days to often break dormancy. The other two species, prairie dropseed and prairie cordgrass, do not have any standardized or published testing methods. To break dormancy in winter wheat, different exposure times (3-day and 5-day) to cold temperatures and growth hormones or chemicals were evaluated for seed crops produced during 2000 and 2001. Chemical treatments used were 1000 ppm and 5000 ppm gibberellic acid, potassium nitrate (first year only), and ethephbn (first year only), and de-ionized water as a control. The 3-day pre-chill (95.8% mean germination) worked as well as the 5-day pre-chill (95.8% mean germination). Gibberellic acid at 5000 ppm had the highest mean percent germination (94.2%) of the chemical treatments. With prairie cordgrass, light and dark, use of growth hormones or chemicals, and various temperature regimes were evaluated to start developing optimum methods for germination testing or reducing dormancy. Results indicated that there appears to be no difference between light and dark treatments. The most promising temperature is an alternating 20-30°C. The chemical of choice would be 0.2% potassium nitrate. Gibberellic acid at 5000 ppm caused abnormalities resulting in stunted root growth. Prairie dropseed was exposed to a pre-chill treatment, varying germination temperature regimes, and growth hormones or chemicals to break dormancy. The seeds were exposed to a pre-chill {5°C) for two weeks and then planted at various temperature regimes with different growth hormones ·or chemicals. A set of each sample for each treatment and temperature was placed straight into the germinators to examine the effect of the pre-chill. The chemicals used were potassium nitrate, 500 ppm, 1000 ppm, and 5000 ppm gibberellic acid, 1.0 mM ethephon, and de-ionized water control. The temperature that appears to break dormancy and maintain viability is either 20-30°C or 25°C. The chemical treatment that yielded the lowest dormancy and maintained viability was potassium nitrate or de-ionized water