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Effect of Temparature and Dormancy on Germination of Tall Fescue¹

The effects of alternation and duration of temperature levels on the germination of dormant and nondormant seed of tall fescue (Festuca arundinacea Schreb ‘Fawn’) were evaluated. Dormancy induction and temperature preconditioning of dormant seed were also studied.

Dormancy was greater in seed matured at 15 C compared to that matured at 26.6 C. The expression of dormancy was also more pronounced at a higher germination temperature (26.6 C).

Temperature preconditioning of dorma nt fescue seed was important in relieving dormancy; germination response was essentially confined to imbibing temperatures of 15 C. Preconditioning time was important and 48 days at 1 C, 24 or 48 days at 5 C, and 24 days at 10 C gave near maximum germination response.

Germination of dormant and nondormant seed was influenced differentially by level and alternation of temperature and by the amplitude of temperature fluctuation. For nondormant seed, constant temperature at 20 to 25 C was optimum. For dormant seed, alternating temperatures were more favorable, and the optimum regime was 8 hours at 20 to 25 C and 16 hours at 10 to 13 C with the range of response to temperature being more restricted than for nondormant seed. Germination response of dormant seed diminished as the time period at the higher temperature increased.

The germination responses of dormant seed observed in this study indicate that at least two physiological phenomena may be involved. The thennogradient response could be a combination of the effects of temperature on the germination processes, per se, and on the metabolic and/or physical processes involved in dormancy. In nondormant seed, only the rate and extent of germination was affected by the temperature regime.

Key Words: Festuca arundinacea Schreb. • Stratification • Thermogradient

² Senior research officer (seed production) Box 1671, G. P. O., Adelaide, South Australia, 5001; research plant physiologist USDA-ARDS, State University Station, Fargo, ND 58102 (formerly with the Agricultural Marketing Institute, ARS-USDA, Beltsville, MD 20705): and professor of crop physiology, Dep. of Agronomic Crop Science, Oregon State Univ., Corvallis, OR 97331, respectively.

Received for publication July 1, 1974.