The consumption of microgreens has increased due to their having higher levels of bioactive compounds and mineral nutrients than mature plants. The lighting conditions during the cultivation of microgreens, if optimally selected, can have a positive effect by further increasing their nutritional value. Thus, our study aimed to determine the changes in mineral nutrients contents of Brassicaceae microgreens depending on different blue–red (B:R) light ratios in light-emitting diode (LED) lighting and to evaluate their growth and nutritional value according to different indexes. Experiments were performed in controlled environment growth chambers at IH LRCAF, 2020. Microgreens of mustard (Brassica juncea ‘Red Lace’) and kale (Brassica napus ‘Red Russian’) were grown hydroponically under different B:R light ratios: 0%B:100%R, 10%B:90%R, 25%B:75%R, 50%B:50%R, 75%B:25%R, and 100%B:0%R. A 220 μmol m⁻² s⁻¹ total photon flux density (TPFD), 18 h photoperiod, 21/17 ± 2 °C temperature and 60% ± 5% relative humidity in the growth chamber were maintained during cultivation. We observed that an increasing percentage of blue light in the LED illumination spectrum during growth was associated with reduced elongation in the microgreens of both species and had a positive effect on the accumulation of mostly macro- and micronutrients. However, different B:R light ratios indicate a species-dependent response to changes in growth parameters such as leaf area, fresh and dry mass, and optical leaf indexes such as for chlorophyll, flavonol, anthocyanin, and carotenoid reflectance.

Modern apple orchard systems should guarantee homogeneity of fruit internal and external qualities and fruit maturity parameters. However, when orchards reach productive age, a variation of these parameters takes place and mostly it is related to uneven light distribution within the tree canopy. The aim of the study was to evaluate the canopy position’s effect on fruit internal and external quality parameters. This is the first study where all the main fruit quality and maturation parameters were evaluated on the same trees and were related to the light conditions and photosynthetic parameters. Four fruit positions were tested: top of the apple tree, lower inside part of the canopy, and east and west sides of the apple tree. Fruit quality variability was significant for fruit size, blush, colour indices, total sugar content, dry matter concentration, accumulation of secondary metabolites and radical scavenging activity. Fruit position in the canopy did not affect flesh firmness and fruit maturity parameters such as the starch index, Streif index and respiration rate. At the Lithuanian geographical location (55°60′ N), significantly, the highest fruit quality was achieved at the top of the apple tree. The tendency was established that apple fruits from the west side of the canopy have better fruit quality than from the east side and it could be related to better light conditions at the west side of the tree. Inside the canopy, fruits were distinguished only by the higher accumulation of triterpenic compounds and higher content of malic acid. Light is a main factor of fruit quality variation, thus all orchard management practices, including narrow two-dimensional tree canopies and reflecting ground covers which improve light penetration through the tree canopy, should be applied.

Light and nutrients are among the most important factors for sustained plant production in agriculture. As one of the goals of the European Green Deal strategy is to reduce energy consumption, greenhouse growers focus on high-value crop cultivation with less-energy-demanding growing systems. This study aimed to evaluate the effect of fertilization at different light intensities on the growth of lettuce and basil and the activity of the antioxidant system. Sweet basil (Ocimum basilicum, ‘Opal’) and lettuce (Lactuca sativa, ‘Nikolaj’) were grown in a greenhouse supplementing natural light (~80 µmol m⁻² s⁻¹) with lighting at two photon flux densities (150 and 250 µmol m⁻² s⁻¹), 16 h photoperiod, and 20/16 °C day/night temperature in May (Lithuania, 55°60′ N, 23°48′ E). In each light regime treatment, half of the plants were grown without additional fertilization; the other half were fertilized twice a week with a complex fertilizer (NPK 3-1-3). The results showed that the antioxidant activity of basil was most affected by 150 µmol m⁻² s⁻¹ PPFD lighting and the absence of fertilization. Altered antioxidant activity in lettuce in the presence of 250 µmol m⁻² s⁻¹ PPFD additional light intensity and fertilization resulted in higher morphological parameters.

The precise management of the nutrient solution pH is substantial for optimizing the growth and yield of hydroponically cultivated crops. Nutrient solution pH affects the solubility and availability of essential nutrients; however, during hydroponic cultivation, the pH of nutrient solution fluctuates due to unbalanced ion absorption by plants. Nutrient solution pH fluctuations might be passively controlled using a supplementary buffering agent. Nutrient solution characteristics such as pH and buffering agent molarity must be addressed simultaneously. Therefore, in this study, we aimed to evaluate hydroponically cultivated lettuce’s physiological response to minor nutrient solution pH differences and the impact of supplementary buffering agent molarity on its growth, antioxidant activity, and mineral nutrient uptake. Green lettuce (Lactuca sativa (L.)) ‘Hugin’ was cultivated in deep water culture (DWC) hydroponics in a controlled environment replicating common vertical farming conditions, and nutrient solution pH impact within the range of 5.0–6.5 was evaluated every 0.5 pH unit. Initial nutrient solution buffer capacity was enhanced by adding MES (2-(N-morpholino) ethanesulfonic acid) at 0, 1, 3, and 5 mM concentrations. Results show that even small nutrient pH differences are reflected in plant physiological responses, indicating the significance of precise pH management. Even though dry weight accumulation is not affected by the pH 5.0–5.5 treatment, it increases root antioxidant response according to ABTS (2,2-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) radical scavenging activity. An initial nutrient solution buffer capacity increment with 3 mM of MES (2-(N-morpholino) ethanesulfonic acid) supplementary buffering agent resulted in a 17% yield increase compared to a nutrient solution without an additional buffering agent. MES buffer can provide adequate, passive, and precise nutrient solution pH control within the pH range of 6.0–6.5.

The study aimed to determine the changes in phenolic compounds content in lettuce (Lactuca sativa L. cv. Little Gem) depending on the preharvest short-term daytime or nighttime supplemental light-emitting diodes (LEDs) to high-pressure sodium lamps (HPS) lighting in a greenhouse during autumn and spring cultivation. Plants were grown in a greenhouse under HPS supplemented with 400 nm, 455 nm, 530 nm, 455 + 530 nm or 660 nm LEDs light for 4 h five days before harvest. Two experiments (EXP) were performed: EXP1—HPS, and LEDs treatment during daytime 6 PM–10 PM, and EXP2—LEDs treatment at nighttime during 10 AM–2 PM. LEDs’ photosynthetic photon flux density (PPFD) was 50 and HPS—90 ± 10 µmol m⁻² s⁻¹. The most pronounced positive effect on total phenolic compounds revealed supplemental 400 and 455 + 530 nm LEDs lighting, except its application during the daytime at spring cultivation, when all supplemental LEDs light had no impact on phenolics content variation. Supplemental 400 nm LEDs applied in the daytime increased chlorogenic acid during spring and chicoric acid during autumn cultivation. 400 nm LEDs used in nighttime enhanced chlorogenic acid accumulation and rutin during autumn. Chicoric and chlorogenic acid significantly increased under supplemental 455 + 530 nm LEDs applied at daytime in autumn and used at nighttime—in spring. Supplemental LEDs application in the nighttime resulted in higher phenolic compounds content during spring cultivation and the daytime during autumn cultivation.