Light quality modifies the composition of essential oil in thyme (Thymus vulgaris)

Abstract

Objective: To identify the changes in the concentration of the main components of thyme (Thymus vulgaris) essential oil in response to five different LED colors.

Design/Methodology/Approach: A completely randomized experimental design was used. The design included five treatments (white light; blue light; red light; 75% blue light and 25% red light; and 75% red light and 75% blue light) and 10 repetitions, at a 25 μmol m⁻² s⁻¹ luminous intensity, during a 16 h photoperiod. The thyme plants were sown in a pot with a substrate made up of 50% peat, 48% perlite, and 2% vermicompost. Each plant was an experimental unit. The plants were placed in light isolation chambers and subjected to the treatment for 35 days.

Results: The concentration of the main molecules in the essential oil recorded considerable changes between treatments: the concentration of thymol (its main component) increased in the white light treatments, as well as in the red light (75%) and blue light (75%) treatments. In addition, the composition of the essential oil resulting from these treatments is different to the composition reported in the references.

Study Limitations/Implications: The light intensity used in this experiment was lower than the light intensity required for plant growth; however, it was enough to produce changes in the secondary metabolism.

Findings/Conclusions: The changes in the quality of the light modify the composition of the thyme essential oil. Even at a low light intensity (25 µmol m^-2 s^-1), the changes in the spectrum composition under which the plants grow influence the composition of the essential oil.