Biostimulating effect of chitosan and acetic acid on the growth and profile of the essential oil of Mentha arvensis L

Elicitors are molecules that can induce responses in plants, such as the production of secondary metabolites. Mentha arvensis L. is a medicinal plant belonging to the Lamiaceae family with great importance for the worldwide production of essential oil. This work aimed to evaluate the response of elicitor application to the growth and essential oil production of M. arvensis. Two experiments were carried out at different times under nursery conditions with 50 % shading. The preliminary experimental design was completely randomized with three replications and five treatments (distilled water; 1% glacial acetic acid solution; and 0.25 %, 0.5 % and 0.75 % chitosan), and a second experiment (distilled water, 0.25 % glacial acetic acid and 0.06 % and 0.125 % chitosan) was also conducted. In the preliminary experiment, samples were collected 7 days after treatment application and 0 h, 12 h, 24 h, and 7 days after treatment application in the second experiment. Both experiments were evaluated at 7 days concerning the content, yield, and chemical composition of the essential oil. The use of 1% acetic acid to dissolve chitosan caused aerial plant injury, reducing the essential oil yield. The 4-fold reduction in the concentration of acetic acid and low concentrations of chitosan showed biostimulating action. In conclusion, the growth and essential oil and menthol content of M. arvensis undergo changes dependent on the concentration of acetic acid and chitosan. The 0.125 % concentration of chitosan provides greater accumulation of shoots, roots and total dry weights. Plant pulverizes with 0.25 % acetic acid had a higher essential oil content, while maximum menthol content is reached with 0.06 % chitosan.