Light conditions can promote the growth and development of plants and contribute to increase the essential oil production of commercially cultivated medicinal and aromatic species. In view of the great importance of Ocimum gratissimum L., Lamiaceae, as an aromatic plant, the objective of this work was to determine the effect of light intensities (approximately 4, 7, 11 and 20mol m−2 d−1) on growth, foliar micromorphology, essential oil content, yield and chemical composition of O. gratissimum. Biomass production of different organs, root:shoot ratio and leaf mass per area were found to linearly increase with increased light availability, whereas stem dry matter fraction, number of leaves, leaf area and plant height have increased up to 10mol m−2 d−1 and decreased from this value. The tector trichomes density increased with increased light availability, but there was no effect of light treatments on the glandular trichomes density and essential oil content. Regardless of the light level, the major component of the essential oil was eugenol. The essential oil yield per plant increased linearly with light intensity as a direct effect of increased leaf biomass under similar conditions

Espécies vegetais são capazes de ajustar suas características fisiológicas, anatômicas e ultraestruturais aos fatores ambientais, como, por exemplo, a disponibilidade de radiação luminosa incidente. O objetivo deste estudo foi avaliar a influência de diferentes níveis de radiação luminosa na anatomia e ultraestrutura foliar de Ocimum gratissimum L. (Lamiaceae). As plantas foram cultivadas por 93 dias em quatro níveis de radiação fotossinteticamente ativa (20, 11, 7 e 4mol m-2 d-1). O incremento da intensidade de luz proporcionou aumento no espessamento dos parênquimas paliçádico e esponjoso e do limbo foliar, entretanto, a espessura da epiderme não foi alterada. Em relação aos aspectos ultraestruturais, verificou-se aumento no tamanho dos cloroplastos e grãos de amido e um aumento do empilhamento dos tilacoides com a redução da intensidade de luz. As variações anatômicas e ultraestruturais verificadas confirmam a plasticidade fenotípica dessa espécie em função da intensidade de radiação luminosa.

Among the several native Brazilian plant species that have yet to be studied for their medicinal properties is Verbesina macrophylla, popularly known as “assa-peixe”. The popular use of this species for medicinal purposes has been reported in southeastern Bahia State, with leaf tea being used to treat renal and urethral problems with anti-inflammatory and antifebrile activities, and flower tea to treat inflammation. Despite the potential medicinal importance of V. macrophylla, studies of its chemical composition and possible activity in controlling fungi and parasites are scarce and recent. This study tested the biological activity of aqueous extracts of leaves and inflorescences of V. macrophylla on the yeasts Candida albicans and Candida tropicalis, the filamentous fungus Fusarium oxysporum, and the epimastigote form of Trypanosoma cruzi. Inflorescence extract showed an inhibitory activity of 41% for cells of C. tropicalis, causing changes in the plasma membrane, resulting in fungicidal activity. Both aqueous extracts eliminated epimastigotes with a dose/time-dependent relationship, reaching 100% elimination after treatment with 200 μg mL-1 of either, causing cytoplasmic and nuclear disorganization, vacuolization and enlargement of the reservosomes. Although the studied extracts did not present considerable inhibitory activities against the filamentous fungus and yeasts, promising results were seen with the epimastigote form of T. cruzi. These data add industrial and medicinal value to the species. Additional studies are needed, particularly spectrometric analysis of extracts, to elucidate the metabolite(s) responsible for the results of this study.