ARS | Publication request: Effect of Fe and Zn treatments on phenolic compounds in spinach leaves

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 30, 2010
Publication Date: N/A

Technical Abstract: Both minerals and phenolics play a crucial role in maintaining and promoting human health. Although many studies to enhance the concentration of minerals or phenolic compounds in plant-based foods have been conducted, there are few studies elucidating the relationship between minerals and phenolics in plants. Thus, the objective of this study was to monitor the variation of phenolic concentration in spinach (Spinacia oleracea cv. Melody) when grown hydroponically with high Fe or Zn concentration. One week-old spinach seedlings grown with water were cultivated with normal nutrient solution for another week, then transferred, and cultivated with nutrient solution containing 5 to 200 uM Fe (III)-EDDHA, or 2 to 50 uM ZnSO4 for 2 additional weeks. Elevated Fe application inhibited Fe acquisition in spinach roots, and subsequently did not have a significant impact on the accumulation of Fe in spinach leaves. In addition, no significant differences in growth characteristics were observed between control and high Fe treated plants. However, the concentration of total phenolics and individual phenolic compounds decreased along with elevated Fe treatments. Dissimilar with Fe, spinach plants subjected to high-Zn nutrient solution significantly accumulated Zn in the leaves compared to controls. The Zn concentration (1784 ug/g DW) of spinach leaves, following a 50 uM ZnSO4 treatment was over 6 times higher than that in control. With treatments up to 8 uM Zn, Zn concentration of spinach leaves increased without a reduction in growth or phenolic compounds. However, significant growth reduction and chlorosis were observed with Zn treatments greater than or equal to 20 uM. In conclusion, these results suggest that Fe concentration of spinach leaves was highly regulated by roots, and certain Zn treatments induced Zn accumulation without growth reduction and did not affect phenolic concentration in spinach leaves.