Efeito de elicitores bióticos na morfofisiologia e na produção de metabólitos secundários de Lippia alba (Mill.) cultivadas in vitro

Abstract

The genus Lippia belongs to the Verbenaceae family and has about 200 species distributed in South, Central America and Africa. The species Lippia alba (Mill.) N. E. Br. Ex P. Wilson is found in the Brazilian Northeast semiarid; its leaves are rich in essential oil and have proven antimicrobial and antioxidant activity, with relevance in the pharmaceutical and cosmetic industry. In this sense, micropropagation appears as a technique for in vitro multiplication of plants, where explants are introduced in a nutrient medium, which can be supplemented with substances known as elicitors, which aim at modulations in the growth and production of secondary metabolites in plants developed in vitro. Thus, the objective of this work was to evaluate the influence of the application of elicitors on in vitro development and on the production of secondary compounds in Lippia alba. Initially, young cuttings containing nodal segments were removed from parent plants and the process of asepsis started. Then, the nodal segments (1 cm) containing two lateral buds were inoculated in MS medium (Murashige & Skoog, 1962) with half the ionic strength. The explants were kept in a growth room at 25 ± 2 ° C and a 16-hour photoperiod. After the establishment phase, the plants were seeded and inoculated in pots, containing 50 mL of the semi-solid MS medium plus methyl jasmonate (0, 100, 200 and 300 μM L -1), chitosan or yeast extract in the concentrations of: 0, 200, 400 and 600 mg L -1, for 5 days or 10 days. After that period, the nodal segments (explants) were transferred to test tubes containing MS medium in the absence of the elicitor where they remained for 25 days and subsequently the biometric, biochemical, anatomical parameters and quantitative analysis of the essential oil were evaluated. The quantitative data of the experiment were submitted to ANOVA and compared by the Scott-Knott test at 5% probability. It was observed that the elicitation for 10 days affected the growth and development of the plants, and that the addition of 400 and / or 600 mg L-1 of chitosan and 400 mg L-1 of yeast extract for 5 days in the medium promoted the increase in plant height and leaf biomass. In addition, the plants elicited with chitosan showed a higher number of compounds in the essential oil profile compared to the other elicitors and to the control. In this context, for in vitro elicitation of L. alba we indicate the application of 400 and / or 600 mg L-1 of chitosan in the culture medium for 5 days, as these concentrations provided an increase in the growth of the plants, in addition to better strategies to produce secondary metabolites.