Shoot tissue pigment levels increase in ‘Florida Broadleaf’ mustard (Brassica juncea L.) microgreens following high light treatment

The xanthophyll cycle pigments [zeaxanthin (ZEA) + antheraxanthin (ANT) + violaxanthin (VIO)] in plants are vital for energy dissipation of excess absorbed light. It is possible to manipulate xanthophyll cycle pigment levels through exposure to light. The objective of this study was to increase ZEA concentrations in mustard (Brassica juncea L. ‘Florida Broadleaf’) microgreens through exposure to high light just prior to tissue harvest. Mustard microgreen plants were cultured on growing pads in a controlled environment under a 14 h photoperiod under 275 μmol photons m−2 s−1. Upon emergence of the first true leaf, light treatments of: (1) 275 μmol photons m−2 s−1; and (2) 463 μmol photons m−2 s−1 were initiated. Microgreen plants were harvested after light treatments had accumulated 36 h during the photoperiod. Shoot pigments were measured for pigments using HPLC separation. Significant decreases in chlorophyll a (P ≤ 0.001) and b (P ≤ 0.01) concentrations under the 463 μmol photons m−2 s−1 light treatment indicated high light stress had occurred. There were significant decreases in β-carotene (P ≤ 0.01) and neoxanthin (P ≤ 0.001) in the 463 μmol photons m−2 s−1 light treatment; however, lutein concentrations were unchanged. Increases in ZEA (P ≤ 0.001), and ANT (P ≤ 0.01) occurred under the 463 μmol photons m−2 s−1 light treatment. Increasing the ZEA levels in microgreens with a simple change in light management may be an effective way for producers to enhance the nutritional value of this increasingly popular specialty crop.

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► The xanthophyll cycle pigments in plants are vital for energy dissipation of excess absorbed light.
► It is possible to manipulate xanthophyll cycle pigment levels through exposure to light.
► We grew mustard (Brassica juncea L. ‘Florida Broadleaf’) microgreens and exposed them to high light just prior to harvest to determine impacts on xanthophyll pigments.
► Increases in zeaxanthin and antherxanthin occurred after exposure to high light treatment.
► Increasing the zeaxanthin levels in microgreens with a simple change in light management will enhance the nutritional value of microgreens.