Cultivo in vitro sob intensidade e qualidade de luz e de ventilação natural em parâmetros de crescimento e do metabolismo da Mentha Spicata L.

Abstract

Mentha spicata L. (Lamiaceae), popularly known as mint, has high biotechnological and pharmaceutical potential due to its rich phytochemical profile, composed of metabolites with antioxidant, antimicrobial, and antiviral properties, among others. In vitro cultivation allows for precise control of environmental factors capable of modulating plant growth and metabolism. Therefore, this study aimed to evaluate the effects of different irradiances, spectral qualities of light, and natural ventilation systems on the development and production of volatile compounds of M. spicata under in vitro conditions. For this purpose, nodal segments of mint previously established in vitro were used. In the light intensity experiment, the nodal segments were cultivated in MS medium with added sucrose, under intensities of 26, 51, 69, 94, and 130 μmol m⁻² s⁻¹. For light quality, nodals were inoculated in MS medium with sucrose under eight LED spectra: white, yellow, green, blue, red, and the combinations 70% red:30% blue, 50% red:50% blue, and 30% red:70% blue. In the experiment with natural ventilation systems (NVS), nodal segments containing a pair of leaves were cultivated in MS medium without the addition of sucrose, using four ventilation systems: flasks without perforations in the lid (NVS0) and flasks with a microporous membrane containing one (NVS1), two (NVS2), or four (NVS4) holes. After 30 days of cultivation, shoot and second internode length, number of shoots and leaves, dry weight, photosynthetic pigments, phenolic compounds, flavones/flavonoids, and the volatile fraction were evaluated. Intensities of 69 and 94 μmol m⁻² s⁻¹ promoted a greater number of leaves, more balanced morphological growth, and greater dry weight accumulation, especially in leaves and roots. The greatest accumulation of photosynthetic pigments occurred at intensities of 26 and 69 μmol m⁻² s⁻¹. Red light favored the highest levels of phenolic compounds, while the accumulation of flavonoids was maximized under the 30% red:70% blue combination. In general, intermediate intensities promoted the highest levels of total phenolics and flavonoids. The volatile fraction showed a high identification index, with a predominance of oxygenated monoterpenes. Carvone stood out in higher concentrations under the spectral combination of 50% red:50% blue and at an intensity of 94 μmol m⁻² s⁻¹, while limonene was favored by yellow and red light and by lower light intensities. Increased ventilation promoted an increase in the number of leaves, the rooting rate, and the accumulation of total dry weight. The use of two membranes favored the accumulation of photosynthetic pigments, while the levels of total phenolic compounds and flavonoids increased progressively with ventilation. The volatile fraction was influenced by the ventilation systems, with higher concentrations of carvone in treatments SVN0 and SVN1.