Luz e ventilação natural impactam o crescimento e produção de compostos voláteis em Mentha piperita L. micropropagadas

Abstract

Mentha piperita L. is an herb used in cooking and present in some food products, perfumes, personal hygiene cosmetics and herbal medicines. Light intensity and quality generate specific physiological and morphogenic responses. In vitro natural ventilation enables the production of seedlings more resistant to acclimatization. The objective of this study was to evaluate the effect of light intensity, light quality and natural ventilation on the production of biomass and volatile compounds of micropropagated Mentha piperita. Nodal segments of 1 cm of in vitro established seedlings were inoculated. In the first experiment, the explants were grown under light-emitting diodes (LEDs) at intensities of 20, 57, 78, 102 and 139 μmol m-2 s-1. In the second experiment, the explants were grown under white LED; blue; red; 70% blue: 30% red; 30% blue: 70% red; 50% blue : 50% red. In the third experiment, flasks using the natural ventilation system (SVN) with 1 (SVN1), 2 (SVN2), 4 (SVN4) porous membranes on the lids and without membrane (SVN0 - control) were used. All experiments were evaluated 30 days after inoculation, evaluating the length of the largest shoot and 2nd internode, number of shoots, leaf area, number of leaves, dry biomass of leaves, stem and root, in addition to the analysis of photosynthetic pigments, phenols, flavonoids and volatile chemical composition. The data were analyzed with the Sisvar software to compare the means, using the Scott-Knott test at a probability of 5%. In the first experiment, the plants under 20 μmol m -2 s -1 etiolated, but had a higher content of photosynthetic pigments. Cultivation under intensities of 78, 102 and 139 μmol m -2 s -1 indicated greater accumulation of dry biomass of leaves and total. The photon flux density did not influence the contents of menthofuran and pulegone. In the light quality experiment, red LED and 70%V: 30%A stimulated the growth of the stem and the 2nd internode. White, blue, 50%V: 50%A and 30%V: 70%A light benefited the production of dry biomass of leaves and roots. Shoots under the combinations of 50%V:50%A accumulated greater contents of total chlorophyll a and carotenoids. Red LEDs and 70%V: 30%A stimulated the production of menthofuran. In the natural ventilation experiment, the shoots showed greater shoot growth, accumulation of dry biomass of leaves, stem and roots in SVN4 and a higher content of photosynthetic pigments in SVN2. It was concluded that from 78 μmol m -2 s -1 , the seedlings of M. piperita develop a greater number of shoots, leaves and dry biomass of the roots, in addition to growing more vigorously. It is recommended to grow the species under 70% V: 30% A LEDs to obtain seedlings with good shoot development, accumulation of dry biomass of the leaves, production of photosynthetic pigments and menthofuran, an important compound for the perfume industry. SVN4 provides vigorous growth of seedlings in vitro.