Morphophysiological dormancy in Smyrnium cordifolium Boiss: Germination requirements and embryo growth

Smyrnium cordifolium Boiss, a biennial medicinal plant, is generally distributed in the Iranian-Turanian phytogeography region. The knowledge about the seed germination and dormancy of this species is limited. S. cordifolium seeds were collected from the Zagros Mountains in Nurabad city, Lorestan province, western Iran. The study was performed based on 9 consecutive experiments. Each experiment was performed as a completely randomized design. Based on a summary of the results, fresh seeds of S. cordifolium (collected in mid-July, 2016) did not germinate after 30 day incubation at different temperature. The seed viability index was recorded 96 +/- 1.4%; while the embryo was not observed in 4% of seeds. Therefore, 100% of S. cordifolium viable seeds were considered to be dormant. Germination increased by increasing the stratification period and was affected by temperature regimes. Although germination was not observed between 0 and 4 weeks after incubation, it began at 4 weeks of incubation at 5 degrees C and peaked at 16 weeks after incubation. After 16 weeks of incubation under photoperiod (12 h light/ 12 h darkness) conditions, germination percentage was recorded 43% at 5 degrees C, and 8% at 15 degrees C. In addition, applying 200 ppm gibberellin concentration improved the Percentage germination. The effect of continuous darkness on germination of S.cordifolium seeds was also proved. Seeds which were incubated for 16 weeks at 5 degrees C under continuous darkness and photoperiod, germinated 71% and 39%, respectively.

Automated summary

Smyrnium cordifolium Boiss, a biennial medicinal plant, is widely distributed in the Iranian-Turanian phytogeography region. Limited knowledge exists about the seed germination and dormancy of this species. The study revealed that the seeds of S. cordifolium did not germinate after 30 days of incubation at different temperatures, indicating that the seeds were dormant. Increasing the stratification period and temperature regimes had a positive effect on germination. Germination was observed after 4 weeks of incubation at 5 degrees C and peaked at 16 weeks. Darkness and gibberellin concentration also influenced germination.