LED Continuous Lighting Reduces Nitrate Content in Brassicaceae Microgreens

The study was carried out to assess whether continuous lighting (CL) can be used to reduce nitrate content in Brassicaceae microgreens. Arugula (Eruca vesicaria subsp. sativa), broccoli (Brassica oleracea var. italic), mizuna (Brassica rapa var. nipposinica) and radish (Raphanus sativus var. radicula) seedlings were grown in the controlled climate chambers under 16 h or 24 h photoperiod provided by light-emitting diode (LED) or fluorescent (FLU) lamps. At the pre-harvest stage, half of microgreens were treated by CL for 3 days. The results show that nitrogen content was decreased significantly in plants grown under LED CL compared to plants grown under 16 h photoperiod. The highest decrease (by 40 %) was observed in arugula microgreens. In contrast, CL provided by FLU lamps had little effect (decrease by 11 and 6 %) on nitrate content in mizuna and broccoli and no effect in arugula and radish. Pre-harvest treatment by CL resulted in significant decrease of nitrate content in all four plant species. In conclusion, continuous LED lighting applied during microgreen cultivation or at the pre-harvest stage effectively reduces nitrate content in Brassicaceae microgreens

Responses of young cucumber plants to a diurnal temperature drop at different times of day and night

In greenhouse production of a number of vegetable and ornamental plant species, a short diurnal temperature drop in the end of the night or in the morning is commonly used to reduce stem elongation as an alternative to chemical growth retardants. Experiments were carried out to quantify the effects of a temperature drop at different times of the day and night on growth and photosynthetic activity of young cucumber plants. During 6 days plants were exposed daily to a temperature of 10 °C for 2 h at the beginning, in the middle and at the end of the night and day periods. The results have shown that plant response to drop may be qualitatively different in the light and darkness. While strongest effects of drop are observed when it is given in the daytime, for practical application in greenhouses it is more appropriate to reduce temperature at night. However, it may not be strictly necessary for cucumber seedlings to apply drop at the end of the night as it was stated in the literature. Thus, our results may cast doubt on the following statements: (a) temperature drops are not effective when delivered at other times of the day or night (except before sunrise), (b) optimal time for drop effects depends on the daily dynamics of stem and petiole elongation rate. It is rather drop itself is capable of modifying the dynamics of plant growth in the daily cycle.</p

Assessment of Four White Sea Brown Seaweed Extracts as Biostimulants of Plant Growth

The study was aimed on the assessment of extracts from four arctic brown seaweeds (Ascophyllum nodosum, Fucus vesiculosus, Laminaria digitata and Saccharina latissimi) as stimulators of plant growth. Seaweeds were collected from the Rebalda Bay of the White Sea in August 2021. Extracts were obtained by isopropanol maceration method, then vacuum-dried at 40°C and stored at -4°C. Protein, polyphenols, chlorophyll, carotenoids, alginates, mannitol and polysaccharides contents of extracts were determined. Wheat and cucumber seedlings were used as test plants. Extracts from all four brown seaweeds enhanced growth, accelerated development of plants and increased chlorophyll content in leaves. Plant responses to seaweed extracts were concentration-dependent. Higher concentration of A. nodosum and F. vesiculosus extracts inhibited plant growth possibly due to higher phenolic content. The results show that investigated seaweed extracts obtained by isopropanol maceration method with subsequent drying and freezing have proven to be effective in plant growth stimulation

Assessment of Four White Sea Brown Seaweed Extracts as Biostimulants of Plant Growth

The study was aimed on the assessment of extracts from four arctic brown seaweeds (Ascophyllum nodosum, Fucus vesiculosus, Laminaria digitata and Saccharina latissimi) as stimulators of plant growth. Seaweeds were collected from the Rebalda Bay of the White Sea in August 2021. Extracts were obtained by isopropanol maceration method, then vacuum-dried at 40°C and stored at -4°C. Protein, polyphenols, chlorophyll, carotenoids, alginates, mannitol and polysaccharides contents of extracts were determined. Wheat and cucumber seedlings were used as test plants. Extracts from all four brown seaweeds enhanced growth, accelerated development of plants and increased chlorophyll content in leaves. Plant responses to seaweed extracts were concentration-dependent. Higher concentration of A. nodosum and F. vesiculosus extracts inhibited plant growth possibly due to higher phenolic content. The results show that investigated seaweed extracts obtained by isopropanol maceration method with subsequent drying and freezing have proven to be effective in plant growth stimulation

Continuous LED Lighting Enhances Yield and Nutritional Value of Four Genotypes of Brassicaceae Microgreens

The effect of continuous lighting (CL, 24 h) and light spectrum on growth and nutritional quality of arugula (Eruca sativa), broccoli (Brassica oleracea var. italic), mizuna (Brassica rapa. var. nipposinica), and radish (Raphanus sativus var. radicula) were investigated in growth chambers under light-emitting diode (LED) and fluorescent lighting. Microgreens were grown under four combinations of two photoperiods (16 h and 24 h) providing daily light integral (DLI) of 15.6 and 23.3 mol m−2 day−1, correspondingly) with two light spectra: LED lamps and fluorescent lamps (FLU). The results show that fresh and dry weights as well as leaf mass per area and robust index of harvested arugula, broccoli, mizuna, and radish seedlings were significantly higher under CL compared to 16 h photoperiod regardless of light quality. There were no visible signs of leaf photodamage. In all CL-treated plants higher chlorophyll a/b and carotenoid-to-chlorophyll ratios were observed in all plants except mizuna. CL treatment was beneficial for anthocyanin, flavonoid, and proline accumulation. Higher activities of antioxidant enzymes (catalase, superoxide dismutase, ascorbate peroxidase, and guaiacol peroxidase) were also observed in CL-treated plants. In most cases, the effects were more pronounced under LED lighting. These results indicate that plants under mild oxidative stress induced by CL accumulated more non-enzymatic antioxidants and increased the activities of antioxidant enzymes. This added nutritional value to microgreens that are used as functional foods providing health benefits. We suggest that for arugula, broccoli, mizuna, and radish, an LED CL production strategy is possible and can have economic and nutritional benefits