Germination of Aesculus hippocastanum seeds following cold-induced dormancy loss can be described in relation to a temperature-dependent reduction in base temperature (Tb) and thermal time

The effect of moist stratification at cool temperatures on Aesculus hippocastanum (horse chestnut) seed dormancy release and subsequent thermal time requirement for germination has been investigated. Germination performance following over 50 different treatments, each varying in time and temperature of stratification and germination to a total test time of over 3 yr, was used to develop a predictive model for dormancy release and germination. Stratification at 2-16degreesC caused a reduction in base (minimum) temperature for germination (T-b), being fastest at the colder temperatures. Using the sigmoid relationship between rate of reduction in T-b and stratification temperature, seed germination can be predicted in relation to thermal time accumulation above a gradually reducing T-b. Newly shed unstratified seeds, seeds with reduced viability, and seeds on the brink of germination because of T-b being close to stratification temperature, did not conform to the model. T-b is not constant during dormancy release in horse chestnut seeds. A reduction in T-b in response to cold stratification may be characteristic of summer annuals, suggesting future applications for this approach in seed ecology studies.