Effects of cold plasma treatment on growth enhancement and on the chemical composition of sweet basil plants (Ocimum basilicum)

The current report is a continuation of our ongoing studies on the effect of cold plasma treatment on the physical and the biochemical properties of the Ocimum basilicum (sweet basil). Our previous work in this area revealed an enhanced growth effect by plasma treatment as well as higher levels of antioxidant components present in the essential oil extracts recovered from the plasma-treated plants. In the present study, the sweet basil was grown from seeds under controlled conditions with the plants separated into four groups. The first Group A (GA) is a control group where no plasma treatment was applied. In the second Group B (GB), the cold plasma treatment was applied to the seeds only. For Group C (GC-1X) and Group D (GD-2X), in addition to the seed treatment, the growing plants in these two groups received an additional body treatment, which was applied once (for Group C) and twice (for Group D) (weekly), following a standard treatment protocol. The total growing period was 14 weeks at which point the plants were harvested. Results revealed that the plants treated with plasma showed increased growth in their leaves and stems particularly in the later stages of vegetation. The essential oils from the sweet basil were recovered by Soxhlet extraction, and their composition was analyzed quantitatively by GC-FID and GC-MS. The extracts of the essential oil both in the control and plasma-treated plant groups showed five major components: eucalyptol, linalool, estragole, eugenol, and methyl cinnamate. Estragole was found to be in the highest concentration in the leaves, while linalool was the dominant product in the flowers, followed by estragole, eugenol, eucalyptol, and methyl cinnamate. In general, plasma treatment resulted in a significant increase in the concentration of both the estragole and linalool in the leaves, while lower concentrations of these two components were registered in the flowers for the plasma-treated groups.