Investigation of seed germination of wild mustard during cold stratification

In order to investigate the variation in cardinal temperature of wild mustard seed germination during the removal of dormancy, a split plot experiment based on a completely randomized design with three replications was conducted at Seed Research Laboratory of Gorgan University of Agricultural Sciences and Natural Resources in 2017. The main factor was different temperatures (5, 10, 15, 20, 25 and 30 °C) and different periods of chilling (0, 2, 4, 6 and 8 days at 5 °C) were assigned as the sub-factor. To describe the response of germination rate to temperature, a dent function was used. For different germination stages, the base temperature decreased from 2.9 to 3.4 °C in control seeds to 1.5 to 1.8 °C in 4 days chilling. Ceilings temperature in control seeds was 25 °C, which increased to 29.9 to 32.9 °C as a result of 6 chilling for 6 days. Due to cardinal temperature changes, the physiological dormancy of wild mustard is of type I. Dormant seeds originally have the highest germination at low temperatures, and they germinate at high temperatures after elimination of dormancy. Also, the germination temperature range increases. Estimated parameters in this study can be useful in seed bank simulation models and for further studies on wild mustard biology and ecology.