Relações da radiação e ácido salicílico em Lavandula dentata no desenvolvimento e produção de óleo essencial

Abstract

Lavandula plants are known for their rich essential oil in volatile compounds with phytotherapeutic and aromatic properties, are used as essence for the manufacture of perfumes and in folk medicine for the relief of respiratory tract disease symptoms. In Brazil, the most adapted species to the climate is Lavandula dentata L. In some places in the South and Southeast, there was an increase in its cultivation due to the gain in its production, mainly in the sale of its essence and tourism attraction. Currently, the use of substances that promote a positive modification in plant growth and productivity have been studied. The elicitors are compounds that act by causing a simulation of attack in the plant, conferring an increase in the activity of the secondary metabolism, which results in a greater amount of the essential oil content. In addition, elicitors act by increasing plant defense against pathogens and assist plants in overcoming abiotic stresses. Therefore, the present work had as objective to investigate the physiological effects caused by the different light qualities in the red, blue and black meshes in comparison to the full sun and the interaction with the application of salicylic acid in the growth and development of the plant, as well as in the production and chemical composition of the essential oil. The plants were cultivated in four conditions of radiation (full sun, black, blue and red meshes) and two conditions of elicitation, with water spray (control) and with 1mM solution of salicylic acid. During the experiment, biweekly measurements of total plant height were taken to obtain growth charts and to verify the interaction of the radiation in its development. Two applications of the elicitor were carried out with a 15 day interval, during which time samples were collected with 24 and 48 hours after each application to the enzymatic activities. At the end of the experiment, plants were collected for essential oil extraction and dry mass analysis. Elicitation promoted an increase in the essential oil content of Lavandula dentata in all radiation treatments, being more effective in plants that were cultivated in colored meshes. In its chemical composition, there were increases in the amount of 1,8-cineol and linalool when under the effect of salicylic acid. There were significant differences in the height and dry mass of the plants grown in the colored meshes, especially when compared to the full sun. It was observed an increase in the activity of antioxidant enzymes catalase, superoxide dismutase and ascorbate peroxidase when under the effect of elicitation, which justifies the effect of salicylic acid as a stressing agent and promoter of plant defense.