Growth, essential oil content, and content of coumarin in young plants of guaco (Mikania glomerata Sprengel) cultivated under colored nets

Mikania glomerata Sprengel is a medicinal plant widely used in folk medicine, mainly to treat respiratory disorders, which acts by dilating the bronchi, being coumarin one of the substances associated with this effect. Therefore, understanding the physiological behavior of this species and its responses to the environmental conditions is necessary to improve the cultivation methods. In this context, the aim of this work was to evaluate the effect of light spectrum control on growth, the essential oil content, and the content of coumarin in Mikania glomerata Sprengel. Plants were grown for four months under nets with 50% shading in gray, red, blue, and exposed to full sunlight (0%). The essential oil was extracted from fresh leaves through hydrodistillation in a modified Clevenger apparatus. The identification and quantification of coumarin were performed through high performance liquid chromatography (HPLC). The results showed the blue fabric allowed an increase in total dry matter accumulation and leaf area, as plants under red shading presented higher dry matter allocation to the roots. The smallest quantity of dry leaves was observed in plants grown under full sun exposure. Changes were not observed, however, in leaf weight ratio and in root/shoot proportion. The essential oil content of plants grown under blue net was 0.14%, which corresponded to an increase of 142% over the level found in plants grown under full sun exposure, as the coumarin content was not influenced by the net color. These results show that light can be modulated during cultivation, in order to obtain desirable morphological characteristics and maximize the production of active principles in this species.