An Analysis of seed Germination and Dormancy Breaking inSome of the Thymus Species Growing in Iran

Thymus is one of the significant species of Lamiaceae family. This genus has 350 permanent aromatic herbaceous or shrub species with various uses in food, sanitary, cosmetics, and pharmaceutical industries. In the present study, the low germination rate in Thyme samples obtained from the Gene Bank of the Natural Resources Institute along with the seeds collected from the national project of the genetic resources of the medicinal plants were examined using the suggested ISTA strategies, i.e. the dormancy test. The results indicated that the lack of germination in the sample seeds of the Gene Bank and the arena settlement problem relate to the long storage time (seed deterioration) and inappropriate time of seed collection. Although, using tetrazolium test, arelatively high percent of seed viability was obtained, but the result was not confirmed by standard germination test. The results indicated that the appropriate chilling period for dormancy breaking should not exceed one month. With an increase in the chilling time, no significant difference was observed among treatments with respect to the germination. It was also found that the long storage of the seeds (more than 7 years) results in seed deterioration and viability which can be attributed to the factors involved in seed collection such as the time of treatment. It can be concluded that the Thyme seeds which are collected for the Gene Bank must be harvested at maximum physiological maturity to present a high seed quality and storability.