Kale Carotenoids Are Unaffected by, whereas Biomass Production, Elemental Concentrations, and Selenium Accumulation Respond to, Changes in Selenium Fertility

Selenium (Se) is a micronutrient in mammalian nutrition and is accumulated in kale (Brassica oleracea L. var. acephala), which has high levels of lutein and β-carotene. Selenium, lutein, and β-carotene have important human health benefits and possess strong antioxidant properties. The objectives of this study were to determine the influence of different Se [as sodium selenate (Na₂SeO₄) and sodium selenite (Na₂SeO₃)] fertility levels on (1) biomass accumulation, (2) the accumulation patterns of carotenoid pigments, and (3) elemental accumulation in the leaves of kale. Winterbor kale was greenhouse-grown using nutrient solution culture with Se treatment concentrations of 0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, and 3.5 mg Se/L as Na₂SeO₄ and 0.0, 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 mg Se/L as Na₂SeO₃. Increases in either selenate (SeO₄^-2) or selenite (SeO₃^-2) resulted in decreases in kale leaf tissue biomass. Neither of the Se treatments had an effect on the accumulation of lutein or β-carotene in leaf tissues. Increasing SeO₄^-2 significantly increased the accumulation of kale leaf Se; however, leaf tissue Se did not significantly change over the SeO₃^-2 treatments. Increases in SeO₄^-2 affected the leaf tissue concentrations of P, K, Ca, Mg, S, B, Cu, Mn, and Mo, whereas SeO₃^-2 only affected B and S. Growing kale in the presence of SeO₄^-2 would result in the accumulation of high levels of tissue Se without affecting carotenoid concentrations.