Microgreens are young, immature vegetables that contain higher concentrations of active compounds compared to mature vegetables and seeds. Radish microgreens are a good source of antioxidants, phenolic compounds, ascorbic acid, carotenoids, and anthocyanins. The production of microgreens is limited by their short shelf life due to higher dark respiration and accelerated senescence. The study was performed on three radish cultivars (Raphanus sativus L.): purple radish (cvP), red radish (cvR), and green radish (cvG). Radish microgreens were grown in chambers with controlled conditions (24 °C and a photoperiod of 16/8 h) under two types of artificial LED light (45 μmol m−2s−1): under white light (B:G:R) and a blue/red light combination (B:2R). The effect of the two types of light was examined on the 3rd, 7th, and 14th day after storage at a low temperature (+4 °C). The physiological status of the three cultivars of radish microgreens was examined by measuring the contents of total soluble phenolics, ascorbic acid, proteins, sugars, dry matter, anthocyanins, carotenoids, and chlorophyll as well as the total antioxidant activity. The results revealed that radish microgreens’ antioxidant capacity and phytochemical profile depend on the radish cultivar and on the type of LED light used for cultivation. It was shown that B:2R and red cultivar were most beneficial for the synthesis of most of the determined phytochemicals compared to B:G:R, or the purple and green cultivar, respectively. Storage at a low temperature in darkness slowed down most of the metabolic reactions during the first seven days, thus preserving most of the antioxidant activity.

The Japanese knotweed (Reynoutria japonica Houtt.) is considered as one of the most aggressive and highly successful invasive plants with a negative impact on invaded habitats. Its uncontrolled expansion became a significant threat to the native species throughout Europe. Due to its extensive rhizome system, rapid growth, and allelopathic activity, it usually forms monocultures that negatively affect the nearby vegetation. The efficient regulation of partitioning and utilization of energy in photosynthesis enables invasive plants to adapt rapidly a variety of environmental conditions. Therefore, we aimed to determine the influence of light conditions on photosynthetic reactions in the Japanese knotweed. Plants were grown under two different light regimes, namely, constant low light (CLL, 40 μmol/m2/s) and fluctuating light (FL, 0–1,250 μmol/m2/s). To evaluate the photosynthetic performance, the direct and modulated chlorophyll a fluorescence was measured. Plants grown at a CLL served as control. The photosynthetic measurements revealed better photosystem II (PSII) stability and functional oxygen-evolving center of plants grown in FL. They also exhibited more efficient conversion of excitation energy to electron transport and an efficient electron transport beyond the primary electron acceptor QA, all the way to PSI. The enhanced photochemical activity of PSI suggested the formation of a successful adaptive mechanism by regulating the distribution of excitation energy between PSII and PSI to minimize photooxidative damage. A faster oxidation at the PSI side most probably resulted in the generation of the cyclic electron flow around PSI. Besides, the short-term exposure of FL-grown knotweeds to high light intensity increased the yield induced by downregulatory processes, suggesting that the generation of the cyclic electron flow protected PSI from photoinhibition.