Crescimento in vitro de plântulas e acúmulo de arbutina em Origanum majorana L. sob diferentes intensidades, espectros de luz, sistema de ventilação natural e doses de sacarose

Abstract

Marjoram (Origanum majorana L.) is an aromatic herb grown mainly in vegetable gardens. Rich in phytochemicals, such as thymol, carvacrol, tannins, hydroquinone and arbutin, which have therapeutic and cosmetic applications. Micropropagation has been widely used in the multiplication of various species of economic interest, including medicinal ones with recognized pharmacological value. The objective was to evaluate the influence of different growth regulators, light spectra, natural ventilation system and sucrose doses on the in vitro growth of Origanum majorana L. and arbutin accumulation. In the first experiment different concentrations of growth salts (Murashige and Skoog culture medium, 1962) of cytokinins (6-benzylaminopurine and metatopolym) in combination with auxins were evaluated. Based on the results obtained, seedlings grown in MS medium and apical explant provided greater growth. Culture medium supplemented with 6-benzylaminopurine or metatopolym at 2.0 mg/L provided greater sprouting, however arbutin accumulation was inhibited by 6-benzylaminopurine. The combination of AIB and MS/2 medium promoted a higher percentage of rooting. The manipulation of light intensity and quality in in vitro cultivation directly affected both biomass production, photosynthetic pigment content and arbutin accumulation. Lower light intensity, 26 and 51 μmol m-2s-1, provided greater growth and photosynthetic pigment content. However, increasing intensities provided greater accumulation of biomass and arbutin. As for light quality, white, green and red and blue light spectrum combined stimulated greater accumulation of biomass and total chlorophyll content, but only the red monochromatic spectrum promoted higher arbutin content. The ventilation system with four porous membranes and with a sucrose concentration of 15 g L-1 proved to be the best treatment. However, greater accumulation of arbutin was favored in photomyxotrophic cultivation in medium supplemented with 30g L-1 of sucrose. Ventilation system and light spectra affected growth, concentration of photosynthetic pigments and arbutin accumulation in vitro, with higher values observed in red monochromatic light cultivation. The present research allowed greater knowledge of the species about its cultivation and production of secondary metabolites in vitro.