Cultivo in vitro de Aeollanthus suaveolens Mart. ex Spreng. (Lamiaceae): intensidade, qualidade de luz e sistema de ventilação natural

Abstract

The species Aeollanthus suaveolens Mart. ex Spreng. is a medicinal plant which has important therapeutic properties, such as anticonvulsant, sedative, anti-inflammatory, and antimicrobial action. There were no studies related to its in vitro cultivation in the consulted literature. Micropropagation of medicinal plants has several advantages over conventional cultivation, such as the possibility of obtaining high quality plant material and also optimizing the production of secondary metabolites. However, understand how the environmental factors affect the in vitro growth of these species is necessary. Thus, the objective of this study was to evaluate the effect of intensity, light quality, and natural ventilation system on the growth and production of photosynthetic pigments in Aeollanthus suaveolens. Three experiments were carried out: In the first one, nodal segments were used, which were grown under the light intensities of 20, 57, 78, 102, and 139 μmol m -2 s -1 , obtained using Light Emitting Diodes (LEDs). In the light quality experiment, nodal segments were cultivated under yellow; white; green; blue; red; 1 blue:2 red; 2 blue:1 red; 1 blue:1 red, and cold white fluorescent lamp. In the third experiment, nodal segments were grown under conventional system (SC) and under natural ventilation system with one (SVN1), two (SVN2), and four porous membranes (SVN4). In all three experiments, plant growth and the concentration of photosynthetic pigments were evaluated. The intensities above 78 µmol m -2 s -1 supported a better growth of this species, presenting a higher accumulation of dry matter, especially in the intensity of 139 µmol m -2 s -1 . While the production of photosynthetic pigments (chlorophyll a, b, total, and carotenoids) were larger under 20 µmol m -2 s -1 . The green light provided greater shoot growth and longer root length. Seedlings cultivated under white LED spectrum presented a greater number of leaves and roots, as well as a greater production of leaf dry matter and stem dry matter. The fluorescent lamp promoted greater accumulation of root dry matter and total dry matter. Seedlings grown under yellow light had higher production of chlorophyll a, total and carotenoids. The highest concentration of chlorophyll b was observed in plants under white LED light. The natural ventilation system with 4 membranes provided higher value for all evaluated growth parameters (numbers of shoots, leaves and roots, shoot length and longest root). Regarding photosynthetic pigments content, the increase in the gas exchange increased the pigment production of the plants. Adjustments of brightness and the use of natural ventilation system are an effective alternative for an in vitro propagation of this species. Intensities above 78 µmol m -2 s -1 , white light spectrum (obtained with LED light bulbs), and the increase in gas exchanges, using a natural ventilation system with four membranes, are more appropriate for the micropropagation of A. suaveolens.