Increased biomass and salicylic acid elicitor activity in fennel (Foeniculum vulgare Miller)

Abstract Fennel is a medicinal and aromatic plant that is commonly used in Brazilian cuisine and in the manufacture of cosmetics. The exogenous application of salicylic acid (SA) can act on the hormonal action stimulating plant growth and development and the induction of plant defense responses under stressful conditions. The objective of this study was to determine the effect of the foliar application of SA on the production of biomass and synthesis of secondary compounds in fennel plants. For this purpose, an experiment was carried out in potted plants in a greenhouse with the application of SA at concentrations of 0, 0.25, 0.50 and 1.00 mM, 20 days and 90 days after transplanting the seedlings to the pots. The effect of SA on the metabolism of the fennel plants was evaluated using growth and biochemical parameters. The exogenous application of SA increased the plant shoots dry weight at the concentration of 0.50 mM, whereas an improved dry root mass and root/shoot ratio was achieved with the concentration of 0.25 mM. The elicitor effect was observed at 0.25 mM of SA, resulting in greater economic value of the biomass due to the higher production of secondary compounds, such as phenolic compounds and flavonoids. In addition, an increase in antioxidant activity of the plant extracts and of the essential oil content of the species was obtained at the concentration of 1.00 mM