Exploring the efficacy of hormonal treatments and pre-sowing techniques on seed germination of Salvia rosmarinus Spenn

Abstract

Salvia rosmarinus Spenn. (Rosemary) holds significant value in medicinal and aromatic applications, serving as a key ingredient in pharmaceuticals, food products, and cosmetics. While many plant species benefit from seed-based propagation, S. rosmarinus poses a challenge due to its mucilaginous seed coating. As a result, germination rates often remain low, ranging from 10 % to 20 %, leading to irregular crop establishment. This study aimed to explore the efficacy of hormonal and other pre-sowing treatments on seed germination of S. rosmarinus. Four distinct treatments were evaluated including physical (sandpaper scarification, dry heat, hot and cold water stratification), chemical (sulphuric acid, hydrogen peroxide, and potassium nitrate), hormonal treatments (GA₃, IAA, and BAP), combination of pre-chilling and hormonal, as well as different potting media combinations, which were compared against an untreated control. All pre-sowing seed treatments, except for hot water, dry heat, chemical treatments, and nanozim, resulted in increased seed germination percentages in S. rosmarinus compared to the control group. Among the different treatments, the combination of pre-chilling + GA₃ and pre-chilling + soil: sand (1:1) treatment resulted in the highest germination percentages of 59.33 % and 63.83 %, compared with those in the control where the germination was 6.83 % and 0.67 %. Potassium nitrate (0.3 % for 3 min) was found to be the most effective chemical treatment with a germination percentage of 24.83 % and seedling vigor index of 3.93 ± 0.69. Pre-chilling treatment for 21 days was the most successful physical treatment, with a germination percentage of 36.66 % and a mean germination time of 17.45 ± 1.34 days. The germination percentage improved with increasing GA₃ concentration up to 150 ppm, beyond which a decline in trend was seen. These findings suggest that understanding the seed germination ecology of S. rosmarinus is crucial for developing seed germination protocols that can enhance mass multiplication with a shorter germination period, ultimately increasing the species' regeneration capability and preserving its variety in nature. This practical and economical approach can help to achieve consistent germination and seedling emergence in nursery raising as well.