| چکیده انگلیسی مقاله |
Extended abstract Introduction: Conditional dormancy (CD) is known as a dynamic series or continuum of states between dormancy (D) and nondormancy (ND), a stage at which seeds germinate over a narrower range of environmental conditions than do ND seeds. Conditional dormancy is presented in some species with nondeep physiological dormancy (nondeep PD). However, primary conditional dormancy was present in some freshly harvested seeds. The purpose of this research was to investigate whether freshly harvested oilseed rape seed has non-dormancy or conditional dormancy Materials and Methods: In order to the investigation of primary conditional dormancy in oilseed rape produced in Golestan and Mazandaran provinces, a factorial experiment was conducted based on a completely randomized design with four replications at the seed technology laboratory of Aburaihan campus, University of Tehran, Iran, during 2018. In this experiment, seeds of rapeseed were collected from 20 different locations in Golestan and Mazandaran provinces. Then, the germination test was carried out at different temperatures (5, 15, 20, 30, 35°C), and the percentage and seed germination rate were recorded. In order to break seed dormancy, two treatments were used; gibberellic acid and After-ripening. For After-ripening treatment, seeds were stored in a paper bag in a dry and dark environment for 6 months. In order to apply the gibberellic acid treatment, a solution of 100 parts per million (PPM) of gibberellic acid was prepared and added to the Petri dishes, then the percentage and rate of germination were recorded. Results: The results showed that freshly harvested seed had primary conditional dormancy and germinated in a narrow range of temperature conditions. Also, cardinal temperatures for freshly harvested seeds were 4.45 and 27.8 for bases and ceilings, respectively. After exposition to gibberellic acid and after-ripening treatments, seeds germinated in a wider range of temperature and base and ceiling temperatures reached to 1.74 and about 40°C, respectively. Thus, germination percentage of seeds treated with gibberellic acid and after-ripening also increased at high and low temperatures, and the increase was higher in germination percentage at high temperatures than in low temperatures. As well as, the effect of gibberellic acid treatment was more than after-ripening treatment on the release of dormancy, and after-ripening treatment had an intermediate effect between the gibberellic acid and freshly harvested seeds. Conclusion: According to the results of this experiment, the application of gibberellic acid and after-ripening treatments resulted in breaking dormancy of freshly harvested seeds and increased germination temperature range at high and low-temperature .between two treatments, gibberellic acid had the greatest effect on breaking dormancy and increasing temperature range. Among the cultivars, these changes were maximum in the germination capacity of Hyola 50 and Trapar cultivars and Hyola 401 had minimum changes. Highlights: 1- Conditional dormancy of oilseed rape cultivars under different environmental conditions was investigated. 2- Application of gibberellic acid and After-ripening treatments resulted in breaking primary conditional dormancy in oilseed rape cultivars. |