Genotype-Specific Modulatory Effects of Select Spectral Bandwidths on the Nutritive and Phytochemical Composition of Microgreens

Abstract

Advanced analytical data on microgreens' response to different light spectra constitutes a valuable resource for designing future crop-specific spectral management systems. The current study defined variation in productivity, nutritive and functional quality (mineral-carotenoid-polyphenolic profiles and antioxidant capacity) of novel microgreens (amaranth, cress, mizuna, purslane) in response to select spectral bandwidths (red, blue, blue-red), and appraised clustering patterns configured by the genotype-lightspectrum nexus. Growth parameters dependent on primary metabolism were most favored by blue-red light's efficiency in activating the photosynthetic apparatus. Nitrate accumulation was higher under monochromatic light owing to the dependency of nitrite reductase on the light-driven activity of PSI, most efficiently promoted by blue-red light. Although mineral composition was mostly genotype-dependent, monochromatic red and blue lights tended to increase K and Na and decrease Ca and Mg concentrations. Lutein, β-carotene, and lipophilic antioxidant capacity were generally increased by bluered light putatively due to the coupling of heightened photosynthetic activity to increased demand for protection against oxidative stress; the disparate response however of purslane highlights the importance of genotype specificity in these responses and calls for additional investigation. Analysis of polyphenols by Orbitrap LC-MS/MS revealed substantial genotypic differences. Most abundant phenolics were chlorogenic acid (x = 5503 µg g −1 dw), feruloylquinic acid (x = 974.1 µg g −1 dw), and caffeoyl feruloyl tartaric acid (x = 993 µg g −1 dw). Hydroxycinnamic acids accounted for 79.0% of the mean total phenolic content across species, flavonol glycosides for 20.7%, and flavone glycosides for 0.3%. The general response across species was a decrease in individual polyphenolic constituents, particularly flavonol glycosides, and total polyphenols under blue-red light. The pronounced effectiveness of monochromatic blue light in eliciting synthesis of flavonoids could be linked to their capacity for absorbing shorter wavelengths thereby quenching generated photo-oxidation potential. The light-induced stimulation of the phenylpropanoid pathway by monochromatic blue light through epigenetic mechanisms or redox signaling in the photosynthetic apparatus warrants

Variation in Macronutrient Content, Phytochemical Constitution and In Vitro Antioxidant Capacity of Green and Red Butterhead Lettuce Dictated by Different Developmental Stages of Harvest Maturity

“…In another work, rutin in coriander was a dominant phenolic acid in the microgreens stage [5], which is in harmony with our work. Chlorogenic acid was also highest among phenolic acids in Kyriacou et al [6] and 10-fold higher in red amaranth and dark green purslane than in green mizuna and cress, the same as red Salanova in this work. Chlorogenic acid was higher in microgreens than in leafy green buckwheat, whereas rutin was not significantly different between the two maturity stages, but quercetin and total polyphenol content were higher in leafy greens' buckwheat [46].…”

“…In fact, when commercial maturity is closer, nitrate concentration rises, due to leaves' self-shading which reduces light incidence and nitrate reduction [27], which reflects the higher value in our mature leaves compared to microgreens lettuce. On the other hand, the sodium concentration in the lettuce microgreens studied in our work is expected, since in the previous works of Kyriacou and coworkers [5,6] on 17 different species and cultivars of microgreens, sodium ranged from 0.66 in amaranth to 12.02 g kg −1 dw in Mizuna. Similarly, low values of sodium in mature leaves are in line with the results obtained by El-Nakhel et al [9] when green and red Salanova where cultivated in hydroponics under the same climate conditions.…”

“…As described by Kyriacou et al [6] 100 mg of lyophilized Salanova material was used to extract polyphenols. Briefly, these latters were quantified and separated through an UHPLC system (UHPLC, Thermo Fisher Scientific, Waltham, MA, USA) equipped with a Dionex Ultimate 3000 Quaternary pump and a thermostated Kinetex 1.7 µm biphenyl (10 × 2.1 mm) column (Phenomenex, Torrance, CA, USA).…”

“…Indigenous populations rely largely on medicinal plants as remedies and edible plants for health support [2], while in the rest of the world plants are demonstrating a huge comeback in the context of healthier lifestyles, particularly as functional foods endowed with bioactive phytochemicals [4]. Driven by these emerging trends in human nutrition connected to physical well-being and nature's legacy as provider of healthier and nutritional foods [2,[4][5][6], agriculture is switching from cultivation for food to cultivation for health. Aside from primary metabolites, plants manufacture innumerable compounds via the secondary metabolism.…”

“…In view of recent research based on human trials asserting that dietary antioxidants are crucial in regulating responses to inflammation and the immune system at cytological level [17], the increasing consumption of microgreens as phytochemically dense greens [18] invites a closer examination of their comparative composition compared to mature greens. Thus far, few works have addressed the differences in phytonutrient composition between mature plants and microgreens, the majority of which posited that the latter is nutritionally more valuable for human consumption, such as Pinto et al [19], Huang et al [13], Charleboi [17], Kyriacou et al [6,14,15]. To our knowledge, only Pinto et al [19] and Weber [20] compared the mature leaves of lettuce with lettuce microgreens and they addressed solely the comparative mineral profiles.…”