Different Microgreen Genotypes Have Unique Growth and Yield Responses to Intensity of Supplemental PAR from Light-emitting Diodes during Winter Greenhouse Production in Southern Ontario, Canada

Abstract

<jats:p>Low natural daily light integrals (DLIs) are a major limiting factor for greenhouse production during darker months (e.g., October to February in Canada). Supplemental lighting (SL) is commonly used to maintain crop productivity and quality during these periods, particularly when the supply chain demands consistent production levels year-round. What remains to be determined are the optimum SL light intensities (LIs) for winter production of a myriad of different commodities. The present study investigated the growth and yield of sunflower (<jats:italic>Helianthus annuus</jats:italic> L., ‘Black oil’), kale (<jats:italic>Brassica napus</jats:italic> L., ‘Red Russian’), arugula (<jats:italic>Eruca sativa</jats:italic> L.), and mustard (<jats:italic>Brassica juncea</jats:italic> L., ‘Ruby Streaks’), grown as microgreens, in a greenhouse under SL light-emitting diode (LED) photosynthetic photon flux density (<jats:italic>PPFD</jats:italic>) levels ranging from 17.0 to 304 μmol·m<jats:sup>−2</jats:sup>·s<jats:sup>−1</jats:sup> with a 16-hour photoperiod (i.e., supplemental DLIs from 1.0 to 17.5 mol·m<jats:sup>−2</jats:sup>·d<jats:sup>−1</jats:sup>). Crops were sown in a commercial greenhouse near Hamilton, ON, Canada (lat. 43°14′N, long. 80°07′W) on 1 Feb. 2018, and harvested after 8, 11, 12, and 12 days, resulting in average natural DLIs of 6.5, 5.9, 6.2, and 6.2 mol·m<jats:sup>−2</jats:sup>·d<jats:sup>−1</jats:sup> for sunflower, kale, arugula, and mustard, respectively. Corresponding total light integrals (TLIs) ranged from 60 to 188 mol·m<jats:sup>−2</jats:sup> for sunflower, 76 to 258 mol·m<jats:sup>−2</jats:sup> for kale, 86 to 280 mol·m<jats:sup>−2</jats:sup> for arugula, and 86 to 284 mol·m<jats:sup>−2</jats:sup> for mustard. Fresh weight (i.e., marketable yield) increased asymptotically with increasing LI and leaf area increased linearly with increasing LI, in all genotypes. Hypocotyl length of mustard decreased and hypocotyl diameter of sunflower, arugula, and mustard increased with increasing LI. Dry weight, robust index, and relative chlorophyll content increased and specific leaf area decreased in kale, arugula, and mustard with increasing LI. Commercial microgreen greenhouse growers can use the light response models described herein to predict relevant production metrics according to the available (natural and supplemental) light levels to select the most appropriate SL LI to achieve the desired production goals as economically as possible.</jats:p>

Continuous Lighting Promotes Plant Growth, Light Conversion Efficiency, and Nutritional Quality of Eruca vesicaria (L.) Cav. in Controlled Environment With Minor Effects Due to Light Quality

“…Rocket yield was high under the tested conditions for all the light treatments. The amount of fresh produce obtained in our system was higher when compared with the yield recorded for rockets under the previous field and controlled environment conditions (Jones-Baumgardt et al, 2020). A higher yield was, however, reported when the rocket was cultivated under high natural irradiance conditions in floating systems (Petropoulos et al, 2016), with presumably much higher daily light integral (DLI) than the one used in our experiments.…”

“…E. vesicaria was germinated on board the International Space Station (Colla et al, 2007); it was selected among the species suitable for food production in space (Dueck et al, 2016). It is known to be suitable for growth and production under fully controlled growing conditions on both Earth-and space-oriented systems (Jones-Baumgardt et al, 2020;Zabel et al, 2020). Our working hypothesis is that the efficiency of the cultivation of E. vesicaria under indoor conditions can be ameliorated by CL without detrimental effects on the yield and quality.…”

Continuous LED Lighting Enhances Yield and Nutritional Value of Four Genotypes of Brassicaceae Microgreens

“…Microgreens are mainly used by chefs and consumers to enhance the color, flavor, texture, and nutritional value of various foods. Microgreens have a limited postharvest shelf life; therefore, local production, especially for fresh-cut products, represents the most promising production strategy [4]. Several species of microgreens are known for their health beneficial effects as they contain high concentrations of health-promoting phytochemicals [1,5].…”

High Light Intensities Can Be Used to Grow Healthy and Robust Cannabis Plants During the Vegetative Stage of Indoor Production

“…Following initial setup, the PPFD at the top of each plant was measured and recorded twice weekly using a quantum sensor (LI-180; LI-COR Biosciences, Lincoln, NE, USA), and the fixture hang-heights were adjusted accordingly, to maintain consistent canopy-level PPFDs throughout the trial. Although the layout of the experiment was a RCBD, the trial was conducted as a gradient design (Jones-Baumgardt et al, 2020;Rodriguez-Morrison et al, 2021) with each plant treated as an experimental unit and assigned a LI level consistent with their respective accumulated light histories. To this end, the average PPFD (APPFD) each individual plant received over the trial was obtained by computing the light integrals between each bi-weekly PPFD measurement period, summing these integrals over the entire trial to determine a total light integral (TLI, mol•m -2 ), and then back-calculating to determine APPFD by dividing TLI by the total number of seconds of lighting during the trial (i.e., 3600 s•hr -1 × 16 hr Ruter, 1992).…”