Induction of hydrolytic enzyme activities in dormant seeds of Dracocephalum kotschyi Boiss. causes improvement of germination and seedling vigor indices

To overcome the seed dormancy of Dracocephalum kotschyi Boiss., a high-valuable herbaceous and medicinal plant, priming technique was applied using mechanical treatment (scarification, Scr) alone, or in combination with various chemical treatments under two groups viz. group-1: KNO3, KH2PO4, Na2SiO3, and group-2: ethanol, ascorbate, gibberellin, polyethyleneglycol (PEG), and complete Johnson nutrient solution (J.N.S). Results showed that scarification increases alpha-amylase, beta-amylase, dehydrogenase, and protease enzymes activities and consequently causes higher seed germination compared to the control. Notably, significant positive effects were observed when the joint mechanical scarification-chemical-priming was applied. Enzymes' activities and metabolite contents were increased in collective primed seeds, especially at the shorter priming times of group-1 and in Scr-GA3-Cold and SCr-J.N.S treatments of group-2. About 97-100% final germination percentage (FGP) and the first germination on 2nd-3rd day were obtained by Scr-GA3-Cold and SCr-J.N.S followed by the improvement of seedling growth indices. The highest GRI, TI, Vig (I), Vig (II), chlorophylls (Chl), the least mean germination time (MGT), and T50 indices were obtained by Scr-GA3-Cold treatment. In general, the most effective treatments for germination of seed and seedling growth improvement could be sorted as; Scr-GA3-Cold >= Scr-J.N.S > Scr-Ethanol, Scr-KNO3-(3h) > Scr-Asc >= Scr-PEG. The joint scarification + chemical-priming induced hydrolytic enzyme activities were more effective than other treatments and caused the breakdown of D. kotschyi seeds dormancy. Notably, hydrolytic enzyme activities (especially amylases) could be considered an indicator for selecting the best priming treatments in advance before seed planting.

Automated summary

This study investigated the effects of scarification and chemical priming on the dormancy of Dracocephalum kotschyi seeds. The results showed that the joint mechanical and chemical treatment had the best effect, significantly increasing seed germination and seedling growth indices. Hydrolytic enzyme activity can serve as an indicator for selecting the best priming treatment.