The effect of pre-sowing treatments and light on seed germination of Dracocephalum kotschyi Boiss: An endangered medicinal plant in Iran

Abstract

The aim of this study was to investigate the effect of pre-sowing treatments and light on Dracocephalum kotschyi Bioss. seed germination. The following treatments were used: sandpaper; 3, 5 and 10 min soaking in sulfuric acid; 15 min in sodium hypochlorite; 24 h in water, hot water and boiling water; 50, 150, and 250 mg·L−1 of Gibberellic acid; 1000, 2000, 4000, and 6000 mg·L−1 of KNO3, and water (control). The germination rate, germination start (GS), mean germination time (MGT), time to 50% germination (T50) and cumulative germination were determined as germination indices. Root, shoot and seedling length and the vigor index (VI) were evaluated as growth factors at the end of the incubation period. Second experiment was carried out to study the effect of light on seed germination. It was observed that both the physical and chemical scarification methods were effective in enhancing D. Kotschyi seed germination and growth. In the first stage, up to day 20 SA (10 min) and sandpaper scarification treated seed had shown germination more than 70% whereas control seeds did not begin germination until day 20. The highest germination rate was observed with sandpaper (1.77 units) and SA (1.56 units) in compare with other treatments (less than 0.9 units). Also the highest vigor index was found in SA- and sandpaper-treated seeds and the lowest occurred in sodium hypochlorite treatments. The other results showed that light was more effective than darkness for seed germination.