Germination response of Dracocephalum kotschyi to sulfuric acid pretreatment, gibberellic acid, and mycorrhiza at different temperatures

The application of different physical, chemical, and hormonal treatments mainly improves the germination of plants such as Dracocephalum kotschyi Boiss that have a seed dormancy mechanism. However, the interaction effects of germination, temperature, pretreatment with sulfuric acid, treatment with gibberellic acid and mycorrhiza on D. kotschyi germination have not been studied. Therefore, this experiment was performed in vitro to study the effect of seed pretreatment on improvement of germination characteristics of D. kotschyi seed.

The treatments studied in this experiment included (1) pretreatment of seed coat with sulfuric acid (97-95 %, for 10 min) and non-pretreatment (distilled water); (2) different treatments including treatments with concentrations of 0, 250, and 500 mg L-1 gibberellic acid (GA) or inoculation with mycorrhiza suspension in two separate experiments; and (3) two temperature treatments; room and refrigerator (about 4 °C) temperatures. The experiment was performed as a factorial based on a completely randomized design with four replications and different germination and initial seedling growth indices were examined.

Gibberellic acid application at room temperature resulted in a significant increase in germination percentage and rate, whereas there was no significant difference between different levels of gibberellic acid and control at 4 °C. Similarly, the application of 250 mg L-1 GA improved seedling length and seedling vigor index at room temperature. While pretreatment with sulfuric acid significantly reduced germination and seedling growth indices compared to non-pretreatment, inoculation with mycorrhiza suspension in both pretreatment conditions compensated the germination reduction caused by sulfuric acid pretreatment by improving germination. Similarly, while the highest seedling length and vigor were obtained from mycorrhizal treatment at room temperature in non-pretreatment with sulfuric acid, at 4 ° C, inoculation with mycorrhiza also significantly reduced the loss in seedling length and seedling vigor index caused by sulfuric acid application.

According to the findings, it seems that the application of 250 mg L-1 GA at room temperature can be considered to improve the germination trend of D. kotschyi. Also, according to the results, treatment with mycorrhiza in sulfuric acid-free treatment at room temperature can be recommended as optimal conditions to improve the germination of D. kotschyi.

1- The interaction effect of chemical pretreatment with biological and hormonal treatments on the germination of Dracocephalum kotschyi was investigated.
2- The application of gibberellic acid at room temperature improved germination compared to the control, whereas it had no effect on germination at 4 °C.
3- Application of mycorrhiza reduced germination loss caused by pretreatment with sulfuric acid and led to maximum germination and seedling growth.