This work aimed to examine dormancy breaking of Black cumin seed (Nigella sativa). Seeds collected from the Isfahan zone in Iran were subjected to different treatments: (a) concentrated sulfuric acid for 30 and 60 seconds, (b) hot water at 70 and 80°C for 5 and 10 minutes (c) concentrated gibberellic acid for 250, 500, 750, 1000, 1250ppm for 24h (d) three levels of KNO3 (0.1, 0.2 and 0.3% v/v) and (e) 3 different stratification periods (1, 2 and 3 weeks). The best percentage of germination, mean germination time, seedling length, seedling dry weight and vigor index were observed in the case of stratification applied for 3 weeks, but 1 and 2 weeks treatment had no strong effect on dormancy release same as 3 weeks. In contrast to stratification, seeds showed no response to periods of sulfuric acid 98% (v/v) and hot water treatments. All of germination traits of Black cumin increased at all concentration of GA3, but 1250ppm was better than the others. Same as GA3, KNO3 treatment had a positive effect on seed germination in all levels especially at 0.3% v/v. the effect of GA3 and KNO3 were not higher than stratification in 3 weeks. It was concluded that stratification in 3weeks was more effective treatment on studied traits than 1 and 2 weeks and it was a stronger action on breaking dormancy and germination of Black cumin seeds than GA3 and KNO3.
