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The aims of the present study were to evaluate the effects of different ventilation systems and sucrose concentrations on the growth, photosynthetic pigment content, and chemical composition of Mentha arvensis L. and M. viridis L. Photon flux (PPF) and growth were also evaluated based on M. arvensis heterotrophic, photomixotrophic, and photoautotrophic culture systems. Nodal segment explants were cultured on medium with 0, 15, and 30 g L−1 sucrose and four alternative membrane systems (AMS) in culture medium, namely no membrane (NMS), one (AMS1), two (AMS2), and four (AMS4) membranes. Mentha arvensis cultivation on medium containing 15 g L−1 of sucrose and four membrane (AMS4) led to the highest dry weight accumulation. Mentha viridis reached the same result with medium containing 30 g L−1 sucrose and AMS2 and AMS4. Mentha arvensis produced higher chlorophyll a, b and total chlorophyll, as well as carotenoids when cultured on medium with 30 g L−1 of sucrose and AMS4 and M. viridis when cultured on medium with 15 g L−1 of sucrose and AMS4. The NMS without sucrose favored higher pulegone and AMS4 induced higher menthol, menthone, and limonene from M. arvensis cultured in vitro. Furthermore, AMS2 induced menthol production and AMS1 increased trans-sabinene, linalol, and limonene content in M. viridis. Mentha arvensis plantlets cultivated under photoautotrophic system with 130 μmol m−2 s−1 showed improved growth and the highest leaf area. Thus, the recommendation to increase upper biomass and plantlet quality in mint species lies on employing an alternative membrane system under higher PPF. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the effects of different intensities and quality of light and explant type on the growth of and volatile compounds in Lippia gracilis in vitro. The treatments were as follows: light intensities of 26, 51, 69, 94, or 130 µmol m−2 s−1 from fluorescent lamps and light-emitting diode (LED) lamps at different wavelengths, namely, white, red, blue, and combinations of red and blue light at ratios of 2.5:1 and 1:2.5, respectively, and two explant types, namely, nodal and apical segments. On the 30th day of culture on half-strength Murashige and Skoog (Physiol Plant 15(3):473-497, 1962) medium, growth, production of photosynthetic pigments, chlorophyll a and b, total chlorophyll, carotenoids, and volatile constituents (using headspace gas chromatography-mass spectrometry) were analyzed. The light quality and intensity significantly influenced the in vitro growth of L. gracilis. The apical segments were superior in all parameters evaluated compared to nodal segments. The number of segments plantlet−1, root length, and leaf, shoot, root, and total weight were higher with increasing light intensity, especially under the 94 µmol m−2 s−1 treatment, for both explant types. The red light showed the highest leaf (32.28 mg plantlet−1) and total (58.33 mg plantlet−1) dry weight of all the light qualities. Major constituents, namely, ρ-cymene, γ-terpinene, thymol, carvacrol, and E-caryophyllene, were identified, regardless of light conditions. The amount and composition of volatile compounds varied according to light intensity and quality. Low intensity (26 µmol m−2 s−1) increased γ-terpinene content (12.42%) and concomitantly decreased carvacrol (38.52%). Blue LED light showed higher production of carvacrol (48.11%). [ABSTRACT FROM AUTHOR]

Digitalis mariana ssp. heywoodii (P. Silva & M. Silva) Hinz is an important source of bioactive cardenolides, including the promising antiviral agent glucoevatromonoside (GEV). The influence of light on the contents of total cardenolides has been demonstrated for different species of Digitalis. This study evaluated the influence of light spectral quality on the vegetative growth and levels of photosynthetic pigments, total proteins, total cardenolides, and GEV in D. mariana ssp. heywoodii. The process of extraction and quantification of GEV was established using an analytical quality by design (AQbD) approach, applying experimental design and analytical validation. Seedlings were grown for 120 days under photoconverting nets with 50% shading in blue, red, and black colours and under full sun. The use of blue net, followed by red net, resulted in the highest contents of GEV, total cardenolides, proteins, photosynthetic pigments and dry matter in the plants, along with highest root length and leaf area. The advantage of using blue nets over full sun for cultivating D. mariana ssp. heywoodii , herein demonstrated, aggregates new information on the management of this subspecies and corroborates previous data reported for other Digitalis species. [Display omitted] • Photoconverting nets affect Digitalis mariana ssp. heywoodii growth and metabolism. • Blue net promoted the highest accumulation of glucoevatromonoside and cardenolides. • Blue net promoted the highest production of proteins and photosynthetic pigments. • Blue and red nets promoted the greatest plant growth parameters. • Antiviral glucoevatromonoside extraction method optimized by design of experiments. [ABSTRACT FROM AUTHOR]

Green manure can be used as an alternative to animal manure and organic compounds and can also be part of the management practices for medicinal plant production systems. The objective of this study was to use a combination of sunn hemp (Crotalaria juncea) and cattle manure in the fertilization of Thymus vulgaris L. plants to design better production strategies. The effects on vegetative growth, nutrient accumulation, essential oil production and chemical composition, photosynthetic pigments, and antioxidant activity were investigated. On the basis of four rates of cattle manure (0, 3, 6, and 9 kg m−2), additional four rates of green manure (0, 3, 6, and 9 kg m−2 sunn hemp) were added to each rate of cattle manure plus a positive control treatment (chemical fertilizer), totaling 17 treatments. The combination of organic manures (green and cattle manure) as well as the chemical fertilizer positively affected the dry weight of thyme leaves, stems, and roots. The combination of the highest doses of cattle and sunn hemp manure (9 kg·m−2 and 9 kg·m−2, respectively) resulted in an accumulation of total dry weight 10 times greater than that of the treatment without fertilization, which was significantly higher than that of the control treatment (0 kg m−2 cattle manure and 0 kg m−2 sunn hemp). Only application of green manure (Crotalaria juncea) has positive affected in dry weight. Significant increases in total and a and b chlorophylls and carotenoids were observed in thyme plants with the use of organic fertilizers. The essential oil production and chemical composition were improved by organic fertilization. The highest percentage of thymol (65.42%) was obtained in the group with 9 kg m−2 cattle manure and 3 kg·m−2 green manure. The application of both cattle manure and green manure increased the antioxidant activity of thyme, and this activity was correlated with high levels of carotenoids. The combined use of green and cattle manures is an inexpensive way to increase the yield of thyme and its essential oil and thymol production, and it can reduce the use of chemical fertilizers and thus is ecologically sound for the cultivation of medicinal plants. [Display omitted] • Green manure improves the production and quality of thyme cultivation. • Essential oil and thymol are responsive to combined organic fertilization. • Organic fertilizer combination improves growth and antioxidant response. • Cattle manure in thyme fertilization results in better plant performance. • Nutrients in leaves was high under cultivation at the highest organic fertilization. [ABSTRACT FROM AUTHOR]

[Display omitted] • Photon flux density and wavelength affect growth, pigments and volatile compounds. • Light intensity of 139 μmol m−2 s−1 is optimal for the growth of plantlets. • White LED and fluorescent light are effective for growth and dry weight accumulation. • Monochromatic red, blue and yellow lights inhibited growth. • White LED increased linalool, green and yellow monochromatic increased massoia lactone. Aeollanthus suaveolens Mart. ex Spreng. (Lamiaceae) is an aromatic plant of African origin and is widely used in folk medicine due to its anticonvulsant and sedative effects. The aim of the study was to establish whether photon flux density (PFD) and wavelength, provided by light emitting diodes (LEDs), affect plantlet growth, photosynthetic pigment, and volatile organic compound (VOC) accumulation in Aeollanthus suaveolens. Nodal segments were grown under different PFDs (20, 57, 78, 102 and 139 μmol m−2 s−1) obtained with white LEDs lamps and under different LEDs light spectra as follows: white, green, yellow, blue, red, and combinations of red and blue (2.5R:1B; 1R:2.5B; 1R:1B) and cool white fluorescent lamps. The different light intensities affected the growth and production of photosynthetic pigments and volatile organic compounds. Plantlets grown under a PFD of 139 μmol m−2 s−1 showed greater dry weight accumulation and growth than those raised under other PFDs. The chlorophyll and carotenoid contents increased with a PFD of 20 μmol m−2 s−1. Light quality also affected plantlet growth. White LEDs light and fluorescent light were equally effective for growth and dry weight accumulation. Monochromatic red, blue, and yellow lights inhibited growth in Aeollanthus suaveolens. The concentrations of photosynthetic pigments from A. suaveolens plantlets were significantly affected by different wavelengths. Yellow wavelengths favored the production of photosynthetic pigments. The accumulation of VOCs was influenced by PFD and spectral quality. [ABSTRACT FROM AUTHOR]

Lippia rotundifolia Cham. is in the family Verbenaceae and is endemic to the Cerrado. This species is aromatic and characterized by the presence of glandular trichomes on its leaves that are rich in monoterpenes. The objective of this study was to evaluate the growth, photosynthetic pigment production, and chemical composition of L. rotundifolia grown in vitro under different light wavelengths and intensities. The light intensities consisted of five treatments using cool white fluorescent lamps at 20, 54, 78, 88, and 110 μmol m−2 s−1. The light quality consisted of six treatments using light-emitting diodes (LEDs) in different light wavelengths, namely, white, red, blue, and their interactions: 1R:1B, 2.5R:1B, and 1R:2.5B. After 45 days, the biometric parameters, photosynthetic pigment content, and volatile compounds were evaluated. The lower light intensities of 20 and 54 μmol m−2 s−1 generated higher growth, photosynthetic pigment content, and biomass accumulation. Myrcene and pentadecane were highest under light intensities of 88 and 110 μmol m−2 s−1, respectively. The highest limonene and ocimenone levels were obtained at 20 and 54 μmol m−2 s−1 intensity, respectively, and the highest myrcenone content was obtained at 78 μmol m−2 s−1 intensity. Regarding the light wavelengths, the combination of red and blue spectra further stimulated plantlet growth, and the 2.5R:1B combination obtained the best biometric data and total chlorophyll content. The z-ocimenone chemical compound contents were highest under the 1R:2.5B light spectrum. The monochromatic blue spectrum increased the myrcene and limonene content but decreased the myrcenone content, which was increased by red light. The highest pentadecane contents were obtained with the white spectrum and the red and blue combinations. Unlabelled Image • Light intensity and wavelength influenced the growth of Lippia rotundifolia. • Light intensities of 20 and 54 μmol m−2 s−1 promoted higher growth, photosynthetic pigment, and biomass. • Myrcene was affected by the greater light intensity. • Combination of the red and blue spectra stimulated plantlet growth more strongly. • The monochromatic blue spectrum increased the myrcene. [ABSTRACT FROM AUTHOR]