Research Plant Physiologist USDA-ARS Children's Nutrition Research Center Houston, Texas, United States
Disclosure(s): No relevant financial relationship(s) with ineligible companies to disclose.
Objectives: Although a variety of stressors are able to influence the concentration of carotenoids in plant tissues, the impact of stress on bioaccessibility, or the amount made available for absorption by the body, remains poorly defined. We hypothesized that controlled nitrogen and salinity stress would enhance carotenoid bioaccessibility from spinach.
Methods: Four varieties of spinach were grown under controlled environment conditions (22/18 ℃ day/night; 150 μmoles/m2/s photosynthetically active radiation,12-hour photoperiod) and one week after transplant subject to 50% or 75% nitrogen (modified Hoagland’s solution), or a mild salinity treatment (20/10 μM CaCl2/NaCl). After three weeks of treatment, plants were harvested, analyzed for carotenoids, and subject to a three-stage in vitro digestion to determine bioaccessibility. Carotenoids from raw material, digesta, and aqueous fractions were analyzed by ultra high performance liquid chromatography coupled with a photodiode array detector.
Results: Both nitrogen restriction treatments decreased fresh/dry mass and carotenoid bioaccessibility relative to controls. However, the mild salinity treatment increased carotenoid bioaccessibility without affecting total carotenoid concentration in leaf tissues. Low and mild salinity treatments significantly increased total yield compared to control and nitrogen restriction treatments.
Conclusions: Our data suggest that mild nutrient and salinity stress can be leveraged to generate plant foods with greater delivery potential of fat-soluble phytochemicals. Future studies are needed to confirm if these outcomes extend to other leafy greens and result in significant differences in carotenoid bioavailability.
Funding Sources: United States Department of Agriculture - Agricultural Research Service
