Conventional agricultural production faces numerous challenges due to the pronounced effects of climate change, particularly global warming, and drought more than ever before in history, with the primary concern being to produce adequate yields and high-quality, nutritious plant material. Likewise, people are increasingly looking for new sources of food and are becoming aware of the importance of a varied diet and its connection to health. In this sense, stinging nettle (Urtica dioica L.) stands out as a valuable species that is neglected as a food source, as it has a significant content of specialized metabolites, and thus has an extremely high potential for use both nutritionally and pharmacologically, but is still traditionally collected from natural habitats, so it can be of questionable quality and undefined chemical composition. Therefore, sustainable agricultural practices are increasingly shifting to modern hydroponic cultivation methods in greenhouses. The advantage lies in the easier management and control of a number of factors during cultivation (air temperature and relative humidity, balanced and rational fertilization, minimization of nitrate uptake, etc.), ensuring better conditions for the growth and development of nettle according to its needs. The aim of this review is to give an overview of the technology of stinging nettle cultivation in the field and to show the possibilities of cultivation with modern hydroponic techniques to obtain a final product of consistent and uniform quality, high content of specialized metabolites and significant nutritional value. Research on this topic is still sparse but will certainly increase in the future. Therefore, this review provides all the necessary data for such future studies.

Stinging nettle (Urtica dioica L.) is a medicinal and edible plant species with a high economic potential. In most European countries nettle is still not produced commercially but is collected from natural habitats. This plant requires large amounts of nitrogen for its improved growth and satisfactory yield, which can result in accumulation of harmful nitrates and reducing of raw material quality. Mentioned problems can be solved by controlling the amount of nitrogen through fertilization, i.e. introduction of stinging nettle into agricultural production. The aim of this study was to determine the effect of three nitrogen fertilization doses (0, 100 and 200 kg ha-1) on the chemical composition of cultivated nettle in the second year of growing. The harvest of the nettle for consumption in fresh form was carried out before flowering and six harvests were performed. It was found that cultivated nettle is a valuable source of potassium [2.27% K dry weight (dw)], calcium (5.21% Ca dw) and iron (2765 ppm dw). Fresh nettle herb contained high amounts of ascorbic acid [63.75 mg 100 g-1 fresh weight (fw)] and total phenols (732.49 mg GAE 100 g-1 fw), correlated with its high antioxidant capacity (1936.58 mM Trolox L-1 fw). The highest nitrogen dose (200 kg ha-1) increased the content of crude protein and calcium, however resulted in higher nitrate content and lower values of dry matter, iron, total phenols and ascorbic acid. Therefore, fertilization with 100 kg N ha-1 could be recommended in production of nettle with a high nutritional value.

Microgreens are young plants of various vegetables, medicinal and aromatic plants, cereals and edible wild plants that were first associated with nouvelle cuisine as decoration in dishes due to their attractive appearance and strong flavor. Recently, they have become more sought after in the market due to their high nutritional value. This is due to the growing interest of consumers in a healthy lifestyle that includes a varied diet with emphasis on fresh, functional foods. Nowadays, commercial production of microgreens is shifting to modern hydroponic systems due to their numerous advantages, such as accelerated plant growth and biomass production, earlier harvesting, and more production cycles that positively affect yield and chemical composition. Therefore, the aim of this study was to determine the content of specialized metabolites and antioxidant capacity of hydroponically grown alfalfa (Medicago sativa) cv. ‘Kangaroo’, yellow beet (Beta vulgaris var. conditiva) cv. ‘Yellow Lady’, red cabbage (Brassica oleracea L. var. rubra) cv. ‘Red Carpet’, and fennel (Foeniculum vulgare) cv. ‘Aganarpo’ microgreens. The highest content of total phenols (408.03 mg GAE/100 g fw), flavonoids (214.47 mg GAE/100 g fw), non-flavonoids (193.56 mg GAE/100 g fw) and ascorbic acid (74.94 mg/100 g fw) was found in fennel microgreens. The highest content of all analyzed chlorophyll pigments (Chl_a 0.536 mg/g fw, Chl_b 0.248 mg/g fw, and TCh 0.785 mg/g fw) was found in alfalfa microgreens. However, in addition to alfalfa, high levels of chlorophyll a (0.528 mg/g fw), total chlorophyll (0.713 mg/g fw) and the highest level of total carotenoids (0.196 mg/g fw) were also detected in fennel microgreens. The results suggest that microgreens grown on perlite in floating hydroponics have high nutritional potential as a functional food important for human health and therefore could be recommended for daily diet.

Plants have evolved various adaptive mechanisms to environmental stresses, such as sensory mechanisms to detect mechanical stimuli. This plant adaptation has been successfully used in the production practice of leafy vegetables, called mechanical conditioning, for many years, but there is still a lack of research on the effects of mechanically-induced stress on the content of specialized metabolites, or phytochemicals with significant antioxidant activity. Therefore, the aim of this study was to determine the content of specialized metabolites and antioxidant capacity of lettuce and green chicory under the influence of mechanical stimulation by brushing. Mechanically-induced stress had a positive effect on the content of major antioxidants in plant cells, specifically vitamin C, total phenols, and flavonoids. In contrast, no effect of mechanical stimulation was found on the content of pigments, total chlorophylls, and carotenoids. Based on the obtained results, it can be concluded that induced mechanical stress is a good practice in the cultivation of leafy vegetables, the application of which provides high quality plant material with high nutritional potential and significantly higher content of antioxidants and phytochemicals important for human health.

With its quality, intensity, and photoperiod, light is a decisive abiotic factor that directly influences plant biomass and the accumulation of specialized metabolites (SMs). Photosynthetically active radiation (PAR) has significant effects on primary and secondary plant metabolism and thus influences the morphological characteristics of plants and their antioxidant systems. The aim of this study was to investigate the effects of blue, red, and a 50:50 combination of blue and red LED lighting on the SM content in broccoli, mustard, and garden cress microgreens grown in an indoor farm using the zero-acreage farming technique (ZFarming). This research aims to provide valuable insights into the optimization of light spectra to improve the nutritional quality of microgreens, with a focus on sustainable and space-saving cultivation methods. After eight days, the samples were cut in the cotyledon phenophase and analyzed in a fresh state. The microgreens grown under the blue spectrum LED lighting had the highest content of ascorbic acid (112.70 mg·100 g fw⁻¹), total phenolics (412.39 mg GAE·100 g fw⁻¹), and the highest antioxidant capacity (2443.62 µmol TE·L⁻¹). The results show that the highest content of SMs in all the studied microgreens species was accumulated under the blue spectrum LED lighting. This study underlines the favorable influence of the blue spectrum (400–500 nm) on the nutrient content, especially the enhancement of SMs, in the microgreens investigated. Furthermore, the use of supplemental LED lighting proves to be a sustainable and effective means of producing microgreens with superior nutritional properties through the innovative practice of the zero-acreage farming technique.

In addition to its distinct aroma and flavor, because of which it is often used in various foods and dishes, basil has recently become increasingly popular because of its rich and beneficial nutritional composition. The presence of several varieties and cultivars makes it a species rich in many specific phytochemicals, which is why it is increasingly used in phytotherapy. The aim of this study was to analyze and valorize the nutrient composition and morphological characteristics of three different basil cultivars (‘Genovese’, ‘Dark Opal’, ‘Minimum’) under two growing methods, conventional in open field and floating hydropon. The results of morphological and chemical characteristics showed a significant influence of cultivar in both growing methods. The cultivar ‘Genovese’ obtained the highest yield in floating hydropon (4.02 kg/m²), followed by cultivars ‘Minimum’ and ‘Dark Opal’ (2.03 and 1.83 kg/m², respectively), which were 31%, 97%, and 16% higher compared to soil cultivation. Based on the analyzed physicochemical parameters, the highest values of dry matter, total acids, vitamin C, total phenols, and antioxidant capacity were generally determined in all analyzes basil cultivars grown in the open field compared to those grown in floating. Significantly higher values of the analyzed pigment compounds were found for all hydroponically grown basil cultivars.