Indoor production of ornamental seedlings, vegetable transplants, and microgreens

Growing seedlings and transplants (plugs and liners) in plant factories with electric lighting enables control of environments to produce consistent and uniform plants. In addition, as light emitting diodes (LEDs) become common light sources for sole-source lighting in plant factories, the ability to manipulate the photon spectrum makes it possible to elicit desirable quality attributes of transplants. However, the effects of specific wavelengths on plant traits can depend on other wavelengths, light quantity, photoperiod, species, developmental stage, and other environmental parameters. In addition, there can be trade-offs between crop growth (yield) and quality attributes. Therefore, it is challenging to identify and optimize LED lighting for transplant and seedling production, and likely, there is not a “one-size-fits-all” photon spectrum. In this chapter, we discuss recent research findings on how the quality, quantity, and daily duration of sole-source LED lighting influence growth and development characteristics of floriculture and vegetable transplants produced from seed or stem cuttings, as well as microgreens.