Dormancy and germination response of Galbanum seeds (Ferula gummosa) under different hormonal pre-treatments and cold stratification

Galbanum is one of the most important native medicinal plants in Iran, and nowadays the use of its products and derivatives has become widespread in various industries. Thus, the excessive harvest of this species within its natural habitats has increased. Therefore, the species is enlisted as prone to extinction. Due to the lack of information about germination behavior and dormancy alleviating or breaking methods of Galbanum seeds, less attention has been paid to this plant species by seed science researchers. Hence, this study was designed and performed to investigate the effects of different treatments on Galbanum seed dormancy-breaking.

In this study, two Galbanum seed populations were collected from Boyer-Ahmad pastures (Iran, Kohgiluyeh and Boyer-Ahmad Province) and Pakan Bazr Isfahan Company (Iran). Seeds were exposed to a cold stratification test for 120 days and germinability and dormancy breaking responses were studied. Also, seed drying effects on germinability after exposure to stratification treatment were investigated to evaluate the practical aspects of this treatment. The impacts of different hormonal pre-treatments including gibberellic acid (GA3) and cytokines (Kinetin, 6-Benzylaminopurine) at different concentrations on germination and dormancy behaviors were investigated so as to assess the effect of these treatments on seed dormancy breaking.

Results showed that germination/dormancy behaviors of Galbanum populations were different and also the effect of different treatments on seeds germination and dormancy varied. An increase in germination was observed when stratification was applied for up to 60 days on two seed populations, thereafter germination decreased by prolonged stratification. Also, it was revealed that desiccation of the treated seeds after stratification reduced seed germination. Examining the cause of this issue revealed that the most important reason for the decrease in seed germination in long periods of stratification was the germination of seeds in the stratification bed and in other words, the difference in seed dormancy levels in different stratification periods. Seed germination behavior and dormancy breaking were improved significantly in both Galbanum populations when the different concentration of gibberellic acid and cytokinins was used.

The results of this study indicated the existence of different levels of seed dormancy in different Galbanum populations. It was also found that cold stratification and hormonal pre-treatment of seeds can be significantly effective in seed dormancy breaking. Eventually, it was concluded that Galbanum seed dormancy was classified as semi-deep and deep morphological dormancy due to the effects of different treatments.