Microgreens are edible young plants that have recently attracted interest because of their color and flavor diversity, phytonutrient abundance, short growth cycle, and minimal space and nutrient requirements. They can be cultivated in a variety of systems from simple home gardens to sophisticated vertical farms with automated irrigation, fertilizer delivery, and lighting controls. Microgreens have also attracted attention from space agencies hoping that their sensory qualities can contribute to the diet of astronauts in microgravity and their cultivation might help maintain crew physical and psychological health on long-duration spaceflight missions. However, many technical challenges and data gaps for growing microgreens both on and off Earth remain unaddressed. This review summarizes recent studies on multiple aspects of microgreens, including nutritional and socioeconomic benefits, cultivation systems, operative conditions, innovative treatments, autonomous facilities, and potential space applications. It also provides the authors’ perspectives on the challenges to stimulating more extensive interdisciplinary research. Expected final online publication date for the Annual Review of Food Science and Technology, Volume 14 is March 2023. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

For the past decade, migratory beekeepers who provide honey bees for pollination services have experienced substantial colony losses on a recurring basis that have been attributed in part to exposure to insecticides, fungicides, or their combinations applied to crops. The phytochemicals p-coumaric acid and quercetin, which occur naturally in a wide variety of bee foods, including beebread and many types of honey, can enhance adult bee longevity and reduce the toxicity of certain pesticides. How variation in concentrations of natural dietary constituents affects interactions with xenobiotics, including synthetic pesticides, encountered in agroecosystems remains an open question. We tested the effects of these two phytochemicals at a range of natural concentrations on impacts of consuming propiconazole and chlorantraniliprole, a triazole fungicide and an insecticide frequently applied as a tank mix to almond trees during bloom in California’s Central Valley. Propiconazole, even at low field concentrations, significantly reduced survival and longevity when consumed by adult bees in a sugar-based diet. The effects of propiconazole in combination with chlorantraniliprole enhanced mortality risk. The detrimental effects of the two pesticides were for the most part reduced when either or both of the phytochemicals were present in the diet. These findings suggest that honey bees may depend on non-nutritive but physiologically active phytochemical components of their natural foods for ameliorating xenobiotic stress, although only over a certain range of concentrations; particularly at the high end of the natural range, certain combinations can incur additive toxicity. Thus, efforts to develop nectar or pollen substitutes with phytochemicals to boost insecticide tolerance or immunity or to evaluate toxicity of pesticides to pollinators should take concentration-dependent effects of phytochemicals into consideration.

Mustard (Brassica juncea var. “Ruby Streaks”) is a popular microgreen species with rich phenolic and glucosinolate contents. Light-emitting diodes (LEDs) have been increasingly used to promote the content of bioactive compounds in commercially grown plants, particularly in controlled environment agriculture (CEA) settings. The present research aimed to investigate the effect of LED light wavelengths on the phytochemical profiles of the major secondary metabolites [i.e., anthocyanins, non-anthocyanin phenolics, and glucosinolates (GLs)] of Ruby Streaks mustard microgreens. Twenty-six anthocyanins, thirty-five non-anthocyanin phenolics, and six GLs were characterized in Ruby Streaks mustard extracts. Among them, three hydroxycinnamic acid-acylated Cyanidin 3-O-sophoroside-5-O-diglucosides and eight hydroxycinnamic acid-acylated flavonol-O-pentosylglucosides were newly discovered compounds in mustard microgreens. Three light treatments (blue, red, and magenta) were investigated and compared to the white (2700k) control. The red (660 nm) light and magenta (450 + 650 nm) light promoted the accumulation of both total and individual anthocyanin/aliphatic GLs, while the blue (450 nm) light was found to be the dominant factor in the accumulation of non-anthocyanin phenolics. The results suggested the significant and complex effect of lighting conditions on phytochemical accumulation in Ruby Streaks mustard microgreens, thus the potential of modulating nutritional profiles by varying wavelength of the light source.