The increased use of wireless technology causes a significant exposure increase for all living organisms to radio frequency electromagnetic fields (RF-EMF). This comprises bacteria, animals, and also plants. Unfortunately, our understanding of how RF-EMF influences plants and plant physiology remains inadequate. In this study, we examined the effects of RF-EMF radiation on lettuce plants (Lactuca sativa) in both indoor and outdoor environments using the frequency ranges of 1890–1900 MHz (DECT) at 2.4 GHz and 5 GHz (Wi-Fi). Under greenhouse conditions, RF-EMF exposure had only a minor impact on fast chlorophyll fluorescence kinetics and no effect on plant flowering time. In contrast, lettuce plants exposed to RF-EMF in the field showed a significant and systemic decrease in photosynthetic efficiency and accelerated flowering time compared to the control groups. Gene expression analysis revealed significant down-regulation of two stress-related genes in RF-EMF-exposed plants: violaxanthin de-epoxidase (VDE) and zeaxanthin epoxidase (ZEP). RF-EMF-exposed plants had lower Photosystem II’s maximal photochemical quantum yield (F_V/F_M) and non-photochemical quenching (NPQ) than control plants under light stress conditions. In summary, our results imply that RF-EMF might interfere with plant stress responses and reduced plant stress tolerance.

Basil is best known as an aromatic and medicinal herb due to its rich profile of bioactive compounds. While secondary metabolite production, coupled with growth, has been well studied, photosynthesis has often been overlooked in this regard. In this study, we investigate the effect of light intensities of blue, green, red, and white light of semiconductor LEDs up to 10000 µmol m⁻² s⁻¹ on photosynthetic efficiency and primary and secondary metabolism. Chlorophyll fluorescence data indicate that the conversion of light into chemical energy is the same under green, red, and white light, and 35% increased under blue light. Primary metabolism, represented by assimilation rate, shows that blue light has the lowest assimilation, whereas red and (surprisingly) green light have the highest. Light saturation is reached at 1500 µmol m⁻² s⁻¹, while assimilation under green light is maintained up to 5000 µmol m⁻² s⁻¹. The earliest photoinhibition occurred under blue light in comparison to the other light wavelength under investigation. Blue light also enhances the production of phenolic and flavonoid concentrations up to 40% or 100%, respectively. These results show that photosynthesis, photoinhibition, and secondary metabolite production are wavelength-dependent and indicate how energy fluxes between these processes are related.

This study investigates the effects of ultra-high light intensities and varying light spectra on the photosynthetic efficiency and growth of maize (Zea mays saccharata). Photosynthetic rates, transpiration, stomatal conductance, and leaf temperature were measured under white light, monochromatic light, and their combinations. Assimilation rates increased with light intensities up to 5000 PAR, plateaued around 5500 PAR, and declined beyond 8000 PAR. Red light at 300 PAR yielded the highest assimilation rate under monochromatic conditions, while green light significantly boosted assimilation at higher intensities, peaking at 33.5 µmol m^–2s^–1 under 4000 PAR. A 50% mix of white and green light at 2000 PAR enhanced assimilation by 14% compared to white light alone. Red light (630 nm) notably promoted photosynthesis in high PAR combinations. However, increasing green light reduced quantum yield, and higher blue light enhanced non-photochemical quenching. These findings suggest that ultra-high light intensities with specific spectral combinations can optimize photosynthesis in maize, though this does not necessarily translate to enhanced overall plant growth.

In recent decades, the absorption spectrum as well as McCree’s action spectrum (350–750 nm) have served as the primary basis for photosynthesis research. Based on these spectra, it was long assumed that blue and red light may be used more efficiently for photosynthesis than green light. However, recent studies have demonstrated that green light is more effective than previously assumed, particularly at high irradiance conditions. Nevertheless, most studies still rely on the three standard wavelengths: 450, 527, and 660 nm. In this study, the effects of additional wavelengths on photosynthesis at irradiances of up to 5000 µmol m ^- ² s ^- ¹ were investigated in Ocimum basilicum L. using chlorophyll fluorescence analysis as well as gas exchange measurements. Following preliminary experiments that revealed variations in photosynthetic performance with plant age, as well as between leaf layers and the adaxial and abaxial leaf surfaces, a standardized measurement protocol was established and subsequently applied to evaluate the photosynthetic responses to different wavelengths. These wavelengths included deep blue (430 nm), cyan (485 nm), mint green (500 nm), orange (590 nm), and orange-red (625 nm). Unexpectedly, wavelengths within the “green gap” exhibited the highest CO ₂ assimilation rates, followed by deep blue and reddish wavelengths. Additionally, 4000 K neutral white light was supplemented with varying proportions of these wavelengths to determine the optimal white-light composition for photosynthesis. The most favorable results were obtained when white light was supplemented with 25% shorter wavelengths (430–527 nm).

This study evaluated the effects of different LED spectral irradiance ratios on the growth, secondary metabolites, and essential oil characteristics of Ocimum x africanum Lour. cultivated for four weeks under controlled conditions. Four LED lighting treatments with different red, blue, green, ultraviolet A, and far red light ratios, and a treatment in greenhouse as control were used. The constant 16-h photoperiod and light intensity of 220 µmol·m-2·s-1 were maintained. The F2 treatment (UV-A:B:R:Fr = 6.60:45.15:29.23:19.02) promoted the greatest plant height (76.62 cm), chlorophyll a (7.41 mg/100 g, FW), chlorophyll b (4.73 mg/100 g, FW), and total phenolic (25.78 mg/g, FW) concentrations. F1 treatment (B:G:R:Fr = 17.14:29.8:47.4:5.66) produced the significantly higher (p < 0.01) biomass (8.3 ton/ha, FW), oil yield (10.89 L/ha), and carotenoid (3.74 mg/100 g, FW) than the others. Essential oils contained 12–15 compounds, dominated by neral (27.5–37.3%), geranial (41.1–49.9%), and (E)-β-caryophyllene (2.4–9.9%). While the highest contents of oil (0.83 %, DW), anthocyanin (16.50 mg/100 g, FW), and total flavonoid (14.17 mg/g, FW) were obtained under F4 (B:G:R:Fr = 13.85:43.50:39.30:3.35). These findings demonstrate that optimized LED spectra can effectively improve both productivity and phytochemical quality in O. africanum through regulating both primary and secondary metabolism.

This study evaluated the effects of different LED spectral irradiance ratios on the growth, secondary metabolites, and essential oil characteristics of Ocimum × africanum Lour. cultivated for four weeks under controlled conditions. Four LED lighting treatments with different red, blue, green, ultraviolet-A, and far-red light ratios, and a treatment in greenhouse as low-light control were used. The constant 16 h photoperiod and light intensity of 220 µmol·m⁻²·s⁻¹ were maintained. The F2 treatment (UV-A:B:R:Fr = 6.60:45.15:29.23:19.02) promoted the greatest plant height (76.62 cm), and chlorophyll a (7.41 mg/100 g, FW), chlorophyll b (4.73 mg/100 g, FW), and total phenolic (25.78 mg/g, FW) concentrations. F1 treatment (B:G:R:Fr = 17.14:29.8:47.4:5.66) produced significantly higher (p < 0.01) biomass (8.3 ton/ha, FW), oil yield (10.89 L/ha), and carotenoid (3.74 mg/100 g, FW) than the others. Essential oils contained 12–15 compounds, dominated by neral (27.5–37.3%), geranial (41.1–49.9%), and (E)-β-caryophyllene (2.4–9.9%), while the highest contents of oil (0.83%, DW), anthocyanin (16.50 mg/100 g, FW), and total flavonoid (14.17 mg/g, FW) were obtained under F4 (B:G:R:Fr = 13.85:43.50:39.30:3.35). These findings demonstrate that optimized LED spectra can effectively improve both productivity and phytochemical quality in O. africanum through regulating both primary and secondary metabolism.