Nutrition by design: Boosting selenium content and fresh matter yields of salad greens with pre-harvest light intensity and selenium applications

Authors: ZHU, XUDONG - Oak Ridge Institute For Science And Education (ORISE); Yang, Tianbao; SANCHEZ, CHARLES - University Of Arizona; HAMILTON, JEFFREY - University Of Arizona; Fonseca, Jorge

Submitted to: Frontiers in Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/3/2021
Publication Date: 1/5/2022
Citation: Zhu, X., Yang, T., Sanchez, C.A., Hamilton, J.M., Fonseca, J.M. 2022. Nutrition by design: Boosting selenium content and fresh matter yields of salad greens with pre-harvest light intensity and selenium applications. Frontiers in Nutrition. https://doi.org/10.3389/fnut.2021.787085.
DOI: https://doi.org/10.3389/fnut.2021.787085

Interpretive Summary: Selenium (Se) is a mineral which plays an essential role in multiple human metabolic pathways. Plant-based foods contain Se-bound metabolites with unique functionalities for the human metabolism. A survey of lettuce commercially grown in 15 locations across the USA and Canada showed a tendency for Se to accumulate higher (up to 10 times) in lettuce grown along the Colorado river basin region, where the country’s highest incidence of annual sunlight radiation is recorded. Further the effect of sunlight reduction on the Se content of two species of arugula (Eruca sativa cv. ‘Astro’ and Diplotaxis tenuifolia cv. ‘Sylvetta’) was studied. A 90% light reduction for 7 days before harvest resulted in 25% and 33% Se decline in E. sativa and D. tenuifolia respectively. Effect of light intensity on arugula microgreens yield and selenium uptake was also examined under indoor controlled conditions using different light intensities: High intensity (HI), low intensity (LI), and high intensity plus UV-A (HI-UVA) with 0, 1, 5, and 10 ppm Se treatments. The HI and HI-UVA application increased Se accumulation by 25-100% higher than LI, particularly with the two higher Se concentrations in the growth substrate. HI and HI-UVA also produced arugula yields that was 13-18% higher than LI. Interestingly, Se application alone had a profound effect on arugula microgreens yields, with an increase of fresh matter in both E. sativa (>35%) and D. tenuifolia (>45%) when comparing the control to the 10 ppm Se treatment. Our results revealed i) that general data of nutritional composition of foods should be revised for Se to account for the effect of light radiation during plants’ growth, and ii) the benefit of using selective Se-light protocols to boost greens yields and the nutritional value of common fresh salads for growers.

Technical Abstract: Selenium (Se) is a mineral which plays an essential role in multiple human metabolic pathways. Plant-based foods contain Se-bound metabolites with unique functionalities for the human metabolism. A survey of lettuce commercially grown in 15 locations across the USA and Canada showed a tendency for Se to accumulate higher (up to 10 times) in lettuce grown along the Colorado river basin region, where the country’s highest incidence of annual sunlight radiation is recorded. Further the effect of sunlight reduction on the Se content of two species of arugula (Eruca sativa cv. ‘Astro’ and Diplotaxis tenuifolia cv. ‘Sylvetta’) was studied. A 90% light reduction for 7 days before harvest resulted in 25% and 33% Se decline in E. sativa and D. tenuifolia respectively. Effect of light intensity on arugula microgreens yield and selenium uptake was also examined under indoor controlled conditions with different light intensities: ‘High intensity’ (HI, 160 µ mol-2 s-1 for 12 h/12 h light/dark), ‘Low intensity’ (LI, 70 µ mol-2 s-1 for 12 h/12 h light/dark) and ‘High intensity plus UV-A’ (HI-UVA, 12h light of 160 µ mol-2 s-1, and 2h UV-A, 385 nm of 40 µ mol-2 s-1 + 10 h dark) in a factorial design with 0, 1, 5, and 10 ppm Se treatments. HI and HI-UVA boosted 25-100% higher Se accumulation than LI, particularly with the two higher Se concentrations in the growth substrate. HI and HI-UVA also significantly increased arugula yield by 13-18% higher than LI. Interestingly, Se application had profound effect on arugula microgreens yield, with an increase of fresh matter in E. sativa (>35%) and D. tenuifolia (>45%) when comparing the control to the 10 ppm Se treatment. Our results revealed i) that general data of nutritional composition of foods should be revised for Se to account for the effect of light radiation during plant growth, and ii) the benefit of using selective Se-light protocols to boost greens yields and the nutritional value of common fresh salads.