Dormancy release during hydrated storage in Lolium rigidum seeds is dependent on temperature, light quality, and hydration status

The influence of temperature, light environment, and seed hydration on the rate of dormancy release in Lolium rigidum (annual ryegrass) seeds during hydrated storage (stratification) was investigated. In a series of experiments, seeds were subjected to a range of temperatures (nine between 5 degreesC and 37 degreesC), light (white, red, far-red, and dark), and hydration (4-70 g H2O 100 g(-1) FW) during stratification for up to 80 d. Samples were germinated periodically at 25/15 degreesC or constant 15, 20, or 25 degreesC with a 12 h photoperiod to determine dormancy status. Dark-stratification was an alternative, but not equivalent dormancy release mechanism to dry after-ripening in annual ryegrass seeds. Dormancy release during dark-stratification caused a gradual increase in sensitivity to light, but germination in darkness remained negligible. Germination, but not dormancy release, was greater under fluctuating diurnal temperatures than the respective mean temperatures delivered constantly. Dormancy release rate was a positive linear function of dark-stratification temperature above a base temperature for dormancy release of 6.9 degreesC. Dormancy release at temperatures up to 30 degreesC could be described in terms of thermal dark-stratification time, but the rate of dormancy release was slower at less than or equal to15 degreesC (244 degreesCd/probit increase in germination) than greater than or equal to20 degreesC (208 degreesCd/probit). Stratification in red or white, but not far-red light, inhibited dormancy release, as did insufficient (<40 g H2O 100 g(-1) FW) seed hydration. The influence of dark-stratification on dormancy status in annual ryegrass seeds is discussed in terms of a hypothetical increase in available membrane-bound phytochrome receptors.