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Morphological and Photosynthetic Parameters of Green and Red Kale Microgreens Cultivated under Different Light Spectra
Microgreens are plants eaten at a very early stage of development, having a very high nutritional value. Among a large group of species, those from the Brassicaceae family, including kale, are very popularly grown as microgreens. Typically, microgreens are grown under controlled conditions under light-emitting diodes (LEDs). However, the effect of light on the quality of grown microgreens varies. The present study aimed to determine the effect of artificial white light with varying proportions of red (R) and blue (B) light on the morphological and photosynthetic parameters of kale microgreens with green and red leaves. The R:B ratios were for white light (W) 0.63, for red-enhanced white light (W + R) 0.75, and for white and blue light (W + B) 0.38 at 230 µmol m−2 s−1 PPFD. The addition of both blue and red light had a positive effect on the content of active compounds in the plants, including flavonoids and carotenoids. Red light had a stronger effect on the seedling area and the dry mass and relative chlorophyll content of red-leaved kale microgreens. Blue light, in turn, had a stronger effect on green kale, including dry mass. The W + B light combination negatively affected the chlorophyll content of both cultivars although the leaves were significantly thicker compared to cultivation under W + R light. In general, the cultivar with red leaves had less sensitivity to the photosynthetic apparatus to the spectrum used. The changes in PSII were much smaller in red kale compared to green kale. Too much red light caused a deterioration in the PSII vitality index in green kale. Red and green kale require an individual spectrum with different proportions of blue and red light at different growth stages to achieve plants with a large leaf area and high nutritional value.
Evaluation of Bioactive Compounds and Antioxidant Activity of Green and Red Kale (Brassica oleracea L. var. acephala) Microgreens Grown Under White, Red, and Blue LED Combinations
The Content of Phenolic Compounds and Organic Acids in Two Tagetes patula Cultivars Flowers and Its Dependence on Light Colour and Substrate
The main focus of the study was to determine the content of phenolic acids, flavonoids, and organic acids in the flowers of Tagetes patula ‘Petite Gold’ and ‘Petite Orange’. The growth of the plants was assessed depending on the cultivation conditions. The above plants were illuminated with white light, whereas the ‘Petite Gold’ ones with white light enhanced with blue or red light. Both cultivars grew in a two-level-mineral compounds organic substrate. The research showed that the French marigold flowers were rich in phenolic compounds and organic acids. The ‘Petite Gold’ flowers had more bioactive compounds compared with the ‘Petite Orange’ flowers. Three flavonoids, 10 phenolic acids and seven organic acids were found in the ‘Petite Gold’ flowers. The artificial lighting used during the cultivation of the plants showed diversified influence on the content of organic compounds in their flowers. The measurements of the plants’ morphological traits and the number of inflorescences showed that illumination with red light resulted in a better effect. Large plants with numerous inflorescences grew in the substrate with a lower content of nutrients.
The Biometric Parameters of Microgreen Crops Grown under Various Light Conditions
Microgreens are becoming increasingly popular both as horticultural crops and as vegetables consumed by humans. They are classified as foods of high nutritional value. Twenty-eight microgreens crops were grown in a growth chamber under fully controlled conditions in order to determine how different light treatments affected their growth rate. The plants were grown under three light sources emitting red/blue ratios of about 6.7, 0.6, and 1.6 units (Red light, Blue light, and R + B light, respectively). Apart from that, the spectrum contained 10% yellow and orange light and 10% green light. The fresh weight of the plants ranged from 8 (perilla) to 1052 mg (nasturtium), whereas the length ranged for the same plants from 2.0 to 26.2 cm. The nasturtium was particularly strongly distinguished from the other species by the high values of its biometric parameters. The fresh mass of most of the other microgreens ranged from 20 to 100 mg, whereas their height ranged from 5 to 8 cm. Red light caused a significant increase in the fresh and dry weights of more than half of the species. The light spectrum had a lesser influence on the length of the plants. The research results showed considerable differences in the dynamics of growth of commonly cultivated microgreens.