In this study, we investigated the effects of additional ultraviolet radiation (UV) on the main growth fluorescent lamp light on pigment content and essential oil accumulation in sweet basil (Ocimum basilicum L.). Three different UV light sources from light-emitting diodes and discharge lamps, which emit UV in the UV-A (315–400 nm), UV-B (280–315 nm) and UV-C (100–280 nm) ranges, were tested for basil plant growing. The plants, growing under additional UV-A and UV-B from mercury lamps, on the 60th growing day were higher than control plants by 90% and 53%, respectively. The fresh leaf mass of the UV-A irradiated basil plants was 2.4-fold higher than the control plant mass. The dry mass/fresh mass ratio of the UV-A and UV-B irradiated plants was higher by 45% and 35% in comparison to the control plants. Leaf area was increased by 40% and 20%, respectively. UV-C affected the anthocyanin content most strongly, they increased by 50%, whereas only by 27% and 0% under UV-A and UV-B. Any UV addition did not affect the essential oil total contents but altered the essential oil compositions. UV-A and UV-B increased the linalool proportion from 10% to 20%, and to 25%, respectively, in contrast to UV-C, which reduced it to 3%. UV-C induced the eugenol methyl ether accumulation (17%) and inhibited plant growth. Moreover, UV increased the proportion of α-guaiene, β-cubebene and α-bulnesene and decreased the proportion of sabinene and fenchone. Thus, we concluded that UV (except UV-C) used jointly with main light with PPFD 120 ± 10 μmol photons·m⁻²·s⁻¹ for sweet basil cultivation may be justified to stimulate basil growth and optimize the essential oil accumulation.

Investigation is devoted to the optimization of light spectrum and intensity used for red mustard growing. Notably, most of the studies devoted to red mustard growing were conducted on micro-greens, which is not enough for the development of methods and recommendations for making the right choices about the irradiation parameters for full-cycle cultivation. In this study, we tested four models of LED with different ratios of blue, green red and far red radiation intensity: 12:20:63:5; 15:30:49:6; 30:1:68:1, in two values of photon flux density (PFD)—120 and 180 µmol m⁻² s⁻¹—to determine the most effective combination for red mustard growing. The study was conducted in a container-type climate chamber, where the red leaf mustard was cultivated in hydroponics. On the 30th day of cultivation, the plant’s morphological, biochemical and chlorophyll fluorescence parameters, and reflection coefficients were recorded. The results indicated that the PFD 120 µmol m⁻² s⁻¹ had a worse effect on both mustard leaf biomass accumulation and nitrate concentration (13–30% higher) in the plants. The best lighting option for growing red mustard was the blue–red spectrum, as the most efficient in terms of converting electricity into biomass (77 Wth/g). This light spectrum contributes to plant development with a larger leaf area (60%) and a fresh mass (54%) compared with the control, which has a maximum similarity in spectrum percentage to the sunlight spectrum. The presence of green and far red radiation with the blue–red light spectrum in various proportions at the same level of PFD had a negative effect on plant fresh mass, leaf surface area and photosynthetic activity. The obtained results could be useful for lighting parameters’ optimization when growing red mustard in urban farms.

Lighting conditions are an important controller of plant growth and development, and they affect secondary metabolite synthesis. In this research, we explored the effect of additional UV irradiation of various ranges in addition to the main one at PPFD 160 µmol m⁻² s⁻¹ on the accumulation of some secondary metabolites of stevia (Stevia rebaudiana Bertoni). The fresh weight of leaves was slightly higher under additional UV-A and UV-B irradiation compared with the control variant, and the leaf surface area was significantly larger, respectively, by 23.3 and 20.7% than in the control variant, while the rate of photosynthesis did not decrease. Plants under additional UV-B and UV-C irradiation were under the greatest light stress, as evidenced by a decrease in antioxidant capacity by an average of 30% compared to the control and UV-A. The total flavonoid content was significantly higher (by 74%) under UV-B irradiation. The highest concentration of steviol glycoside was observed during budding and flowering under UV-B and UV-C irradiation (by 13.2 and 11.3%, respectively). Analysis of hyperspectral images, chlorophyll fluorescence, and vegetation indices showed light stress increasing under UV-C irradiation, which caused an increase in the relative chlorophyll content, scorches, leaf morphology changes, a CO₂ absorption rate decrease, and plant growth inhibition. UV-B irradiation can be used as an optimal type of irradiation based on a set of indicators.

This research is aimed at the assessing the impact of the ultraviolet radiation in the A, B, and C ranges (as additives to the main light) on general plan condition, the stress experienced by them, the pigment concentration in the leaves and leaf reflective characteristics. Under studying, there were the photo-protective reactions of the purple variety basil plants. The plants were grown in plastic pots in a phyto-chamber equipped with an automatic microclimate system. The phyto-chamber was divided into four compartments where, in addition to the main lighting, there were installed the additional LEDs emitting their radiation in the ranges UV-A, UV-B, and UV-C. Plant reactions were evaluated by the contents of the main pigments as detected by the spectrometric method. Then correlations were revealed between those values and the vegetative indices obtained based on the hyperspectral images. A strong correlation (R² ˃ 0.83) was observed between the values of the vegetative indices ARI and mARI and the anthocyanins concentration in basil leaves. A weak correlation (R² = 0.0479) was found between the ARI and mARI values and the carotenoids index CRI700, which is attributed to the shielding effect of the anthocyanins. Deviations in the results are influenced by leaf surface unevenness, its thickness and density. Additional research is needed including developing reflection indices taking into account the shielding effect of the purple pigments.

The present study has been carried out to determine the effects of four different illuminators with red, far-red, blue, and white light-emitting diodes (LEDs) on the growth, morphology, pigment composition, and chlorophyll fluorescence of spinach (Spinacia oleracea L.) of the ‘Zhirnolistny’ cultivar. We investigated these variants in two photon flux densities, 400–800 nm (PFD) 120 µmol m⁻² s⁻¹ and 180 µmol m⁻² s⁻¹. The studies were carried out in a climate chamber. Plant measurements were carried out on the 30th and 45th days of cultivation. The results showed that during the period of active growth, on the 30th day, spinach plants accumulated 2.6 and 2.4 times more fresh weight in the variant with a higher PFD (180 µmol m⁻² s⁻¹). At the end of the growing season, only a decrease in PFD had an effect on the fresh and dry weight of plants. The highest concentration of chlorophyll on both the 30th and 45th days of vegetation was found when spinach plants were grown under red-blue (RB) LEDs in a spectrum proportion of R70:B30. It was found that the variants had a higher proportion of green radiation in the spectrum of illuminators with PFD 180 µmol m⁻² s⁻¹, and the nitrate content in spinach was slightly lower than in other variants.

Stevia (Stevia rebaudiana Bertoni) is an important source of natural sweeteners. Since its commercial value depends on steviol glycosides, quality assessment primarily involves quantifying these compounds in leaves and shoots. While chromatography is the standard analytical method, it is labor-intensive and time-consuming; it involves multiple processing steps that may cumulatively introduce errors and remains relatively expensive. Although chromatography remains the most accurate method, this exploratory study evaluates the potential of using spectroscopy as an auxiliary method for the approximate assessment of steviol glycoside content. Leaf reflectance spectroscopy could be a simpler and more cost-effective approach. However, relationships between leaf reflectance and steviol glycoside content are indirect and mediated by physiological processes. To account for these indirect dependencies, cumulative UVB exposure was included as an additional feature because it influences both leaf optical properties and plant metabolic processes. A low-cost spectrometer was utilized as the measuring instrument. The study was conducted over a period of three months on 77 S. rebaudiana clones, divided into four groups based on their level of UVB irradiance (control without irradiation, 400, 600, and 800 μW m⁻²). Based on the collected data, linear and polynomial regression, Random Forest, XGBoost, PLSR, and ElasticNetCV models were trained. Cumulative UVB exposure was found to be the most important feature. Of the spectral features, the most informative for assessing the content of steviol glycosides were spectral indicators in the far-red and near-infrared (NIR) ranges. Our results indicate a detectable relationship, with Random Forest being the best-performing model and achieving a moderate predictive performance (R² = 0.66). Despite their limited predictive performance, the models demonstrate that leaf reflectance spectra combined with cumulative UVB exposure contain information related to steviol glycoside content. These findings support further investigation of remote sensing approaches for crop quality assessment.