A preharvest finishing procedure for Lemna to produce high levels of zeaxanthin that is retained post-high-light exposure

• Lemnaceae are exceptionally rich in both protein and essential human micronutrients that oppose the many diseases and disorders associated with chronic inflammation • Lemnaceae combine rapid growth with stress resilience • Pre-harvest high light optimized essential human micronutrient content in low-light-grown Lemna • Six hours of high light induced stable zeaxanthin accumulation in Lemna • This novel pre-harvest finishing procedure enhances resource-use efficiency Development of a productive, nutritious, and low-input food source is needed for humanity's expanding population on Earth and for long-duration crewed space missions. The exceptionally protein- and micronutrient-rich members of the aquatic plant family Lemnaceae are uniquely suited for both purposes. We here introduce a protocol to accumulate large quantities of the carotenoid zeaxanthin that are retained post-high-light exposure. The function of the essential human micronutrients zeaxanthin, lutein, vitamin E ( α -tocopherol), and pro-vitamin A ( β- carotene) are briefly reviewed. Attention is given to the role of zeaxanthin in opposing oxidants (reactive oxygen species), the production of which is further enhanced by space radiation. We report a new preharvest finishing procedure – sudden transfer of Lemna plants grown in low light (200 µmol photons m -2 s -1 ) to high light (1000 µmol photons m -2 s -1 ) for six hours, which rapidly increased and stabilized zeaxanthin content. Unlike terrestrial crops, Lemna possessed a uniquely high protein content when grown in low light and did not experience any adverse effects of the abrupt five-fold increase in light intensity. These findings provide additional justification for Lemnaceae as food crops with applications on Earth as well as for future long-duration human space missions.