Germination Responses of Taraxacum platycarpum Seeds to Temperature

Abstract

Abstract Germination responses of Taraxacum platycarpum seeds to temperature were examined under laboratory conditions to investigate the emergence‐season choice mechanism of the seeds. Almost all the newly collected seeds were non‐dormant. Under constant temperature conditions, maximum percentage germination (approximately 90%) was attained at temperatures 6–16°C, where simple linear relationships were observed between the temperature and the rates of germination, i.e. the reciprocals of the time taken to germinate by seed subpopulations with 10–80% germination. Thermal time required for germination of the subpopulations ranged from 600 Kh (degree Kelvin × hours) to 1500 Kh with a relatively constant base temperature of about 2.5°C. Lower limit temperature for germination was slightly below 6°C. Higher limit temperature for germination has the normal distribution with the mean ±SD of 19±2.5°C. Pre‐exposure of imbibed seeds to temperatures higher than the higher limit temperature for germination, 25 and 30°C, had no effect on the germinability and the rate of germination at a circa‐optimum temperature. Moist chilling treatment at 4°C caused an increase in the variation of germination rate within the seed population, but no evidence for dormancy‐inducing or breaking effects was obtained.