Alterações anatômicas, fisiológicas e fitoquímicas em Mikania glomerata Sprengel. (Guaco) sob diferentes fotoperíodos e níveis de sombreamento

Abstract

The genus Mikania belongs to the family Asteraceae and is composed of about 450 species, around 200 out of those are found in Brazil. Under the medicinal aspect a number of therapeutic properties such as anti-inflammatory and bronchi-dilating are ascribed, coumarinbeingone of the substances associated to this effect. The studies about the environmental factors such as radiation, which interfere on the growing conditions of medicinal species, associated to the morphophysiological alterations and consequently in the synthesis of substances derived from secondary metabolism. Under this context, by the need for a economical exploration of that potential, for the large scale production of Mikania glomerata Sprengel (guaco), the present work was designed to verify the effects of duration and light intensity on the early growth of that species in the production of coumarin and essential oils. In general, the results showed that the level of 30% of shading is the most favorable for the development of plants. In coumarin production, they revealed that on young plants (100 days old) grown in the full sunshine, coumarin content in the leaves was two times as great as that compared with the adult plant cultivated under the same radiation condition. The upper radiation of the plant both for leaves and stempresented an increased content in all the levels of radiation. Relative to essential oil content, it was 70 less in the shading. As to the different photoperiods studied, they showed that of 16 hours to be the most favorable for the development of the plants, as regards coumarin content in the leaves, it was superior to the other treatments relative to the content of essential oils, the photoperiods of 8, 12, 16 and 20 hours, there were no statistic differences. The infrared spectrometry characterization revealed that they did not modify chemical structure of the present metabolites. The variation in the anatomy of leaves was characterized by an increase of leaf thickness and number of stomas according to the levels of shading and photoperiods.