Reguladores de crescimento, qualidade e intensidade de luz, sistema de ventilação natural e análise da fração volátil na micropropagação de Lippia rotundifolia Cham.

Abstract

Lippia rotundifolia Cham. is an endemic Verbenaceae of the Cerrado, aromatic, characterized by the presence of glandular trichomes in its leaves, rich in monoterpenes. Micropropagation has been widely used in the multiplication of several species with medicinal properties with difficulty in the conventional propagation and to obtain a homogeneous material. The objectives of the work were to evaluate the influence of different growth regulators, light spectra, natural ventilation system and sucrose concentrations on the in vitro growth of L. rotundifolia Cham and chemical compounds of the volatile fraction. Based on the results of biasses with growth regulators, it was observed that TDZ at concentrations of 1.5 and 2.0 mg L-1 with or without ANA generated a higher number of shoots compared to all combinations of BAP and ANA , However, a high percentage of hyperhydricity and callus was found. The plant shows high sensitivity to growth regulators, in which high percentages of hyperhydricity and callus formation were observed, which compromised the viability of the seedlings obtained. Based on this, micropropagation through nodal segments could be considered the safest method to obtain viable seedlings (8 to 10 seedlings) free of calluses and hyperhydricity. The manipulation of the intensity and luminous quality in the in vitro culture showed to affect directly both the production of biomass, the content of photosynthetic pigments and the composition of the volatile fraction. The lower light intensities, 20 and 54 μmol m-2s-1, positively affect growth, having a higher content of photosynthetic pigments and accumulation of biomass. As for light quality, combined red and blue spectrum stimulated better plant development, the combination of 2.5R: 1B obtained better biometric data and total chlorophyll content. In the volatile fraction, the light quality interfered less in the composition of the volatile compounds in relation to the luminous intensity.The use of the natural ventilation system using manufactured porous membranes proved to be a more efficient in vitro culture method than the conventional system. The ventilation system with two porous membranes and the sucrose concentration of 15 g L-1 proved to be the best treatment. Regarding the influence of the ventilation system and the concentration of sucrose in the medium on the content of compounds of the volatile fraction, the sucrose seems to interfere more directly. It is evaluated that the study allowed the expansion of knowledge about the species and its in vitro culture. It is hoped that the research may provide subsidies for proposing new studies on this species among others in the Cerrado.