Influence of Growth Regulators in Biomass Production and Volatile Profile of in Vitro Plantlets of Thymus vulgaris L.

In vitro shoots of thyme (Thymus vulgaris L.) were established, and the effects of the auxin indole-3-acetic (IAA) acid and the cytokinins benzyladenine (BA), zeatin (ZEA), and kinetin (KIN) at 1.0, 5.0, and 10.0 μM on rooting, biomass production, and volatile compounds production by these plants were investigated. The volatiles were extracted by solid phase microextraction (SPME) and analyzed by gas chromatography. The highest biomass shoot growth was obtained with BA at 5.0 μM, while IAA at all concentrations tested achieved 100% rooting frequency. The three major compounds were γ-terpinene (22.8−38.8%), p-cymene (13.8−27.9%), and thymol (6.5−29.0%). Quantitative changes of these compounds were observed in response to the effect of varying growth regulators concentrations in the culture medium. Growing Thymus vulgaris L. plants in media supplemented with IAA at 1.0 μM increased volatile compounds such as thymol by 315%. Nevertheless, the same major compounds were produced in all treatments and no qualitative changes were observed in the volatile profile of thyme plants.