Effect of lavender hydrosol on antioxidant activity and growth in Nicotiana benthamiana

The present study is an investigation of lavender hydrosol as a plant growth promoter. We observed its effects on plant growth promotion, antioxidant activity, and the expression of genes related to defense in tobacco plants. Following treatment with lavender hydrosols for 2 weeks, the leaf length, leaf width, and plant height of N. benthamiana plants were 11.37 ± 0.31 cm, 11.07 ± 0.47 cm, and 14.43 ± 0.90 cm, respectively. An assay using 2,2-diphenyl-1-picrylhydrazyl (DPPH) revealed 90.08 ± 1.20% antioxidant activity, and superoxide dismutase (SOD)-like activity was 79.59 ± 3.18% in a 100% ethanol extract of plants treated with lavender hydrosol. We examined the expression patterns of genes involved in antioxidant and plant defense mechanisms at the transcriptional level in N. benthamiana cells; such genes include those that code for superoxide dismutase (SOD), ascorbate peroxidase (APX), phenylalanine ammonia lyase (PAL), nitrate reductase (NR), and nitric oxide-associated 1 (NOA1). All the genes examined were expressed more in the plants treated with lavender hydrosol than in the untreated controls. The results suggest that lavender hydrosol promotes antioxidant activity in plant cells by activating antioxidant and plant defense mechanisms, ultimately promoting plant growth.