Abstract The cultivation of aromatic species to obtain essential oils has great economic importance, presenting an increasing demand from different industrial sectors, especially to menthol mint (Mentha arvensis L.) essential oil, rich in menthol (70-80%). Consortium cultivation has been an important practice in agricultural systems whose land use is necessary, consequently promoting strong competition for light in reduced space. Thus, this study aimed verifying if different light intensities might promote chemical, metabolical and anatomical alterations in menthol mint. Plants were grown in greenhouse at different average of light intensities (137, 254, 406 and 543 µmol photons m2 s1). Samples were collected 43 days after germination and submitted to following analyses: Gravimetric test, photosynthetic pigments, soluble fractions, enzymatic activity, N-total, trichome density and histochemistry and chemometric test based on essential oil chemical profile. Fresh mass gain, trichome density, essential oil content and soluble sugars were positively influenced by light intensity increase. On the other hand, total-N, NO3−-N and pigments content have decreased influenced by light intensity increase. In the secretion from the trichomes, phenolic substances were reported, as well as lipophilic ones in the peltate ones. The increase of oxygenated monoterpenes was favored by light intensity decrease.

Em experimento conduzido em sistema hidropônico foi avaliada a influência da nutrição mineral sobre o crescimento vegetal e a produção de óleos essenciais de Mentha piperita (hortelã). As plantas foram cultivadas em soluções nutritivas, variando os teores de N e P, sendo: 120 e 16; 60 e 16; 120 e 4; 60 e 4 mg L-1 de N e P para os tratamentos 1; 2; 3 e 4 respectivamente. O maior rendimento em óleos essenciais ocorreu aos 29 DAT (dias após o inicio dos tratamentos) para as plantas cultivadas nas condições do tratamento 4; Em contrapartida, houve maior produção de biomassa aos 64 DAT (em todos os tratamentos). As plantas sob maiores doses de N apresentaram menor rendimento de óleo essencial; no entanto, houve maior ganho de biomassa. Observou-se uma diminuição gradual no rendimento de óleo essencial ao longo do ciclo da planta e uma relação inversa entre o peso de folhas e o rendimento de óleo. Os resultados deste trabalho mostram que aos 29 DAT em cultivo hidropônico as plantas de hortelã estão aptas para serem colhidas, com o objetivo de produção de óleo essencial, o que significa redução no tempo de colheita e economia no processo de produção.

An experiment was carried out, using a hydroponic system to study the effect of plant nutrition regimes on the plant growth and the production of essential oils in Mentha piperita (mint). Plants were grown in nutrient solutions with varying levels of N and P: 120 and 16; 60 and 16; 120 and 4; 60 and 4, mg L-1 of N and P in the treatments 1; 2; 3 and 4 respectively. Plants of the treatment 4 (29 days after starting the treatments, DAT) presented the highest production of essential oils. However, plants presented the highest biomass production at 64 DAT. The higher the N levels in the nutrient solution, the lower the production of essential oils. Higher N inputs resulted in higher total biomass. There was a negative relationship between the plant cycle and the production of essential oils. Mint plants grown in hydroponics systems can be harvested at 29 DAT for the production of essentials oils, saving time and costs of production.