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Effect of zinc sulphate (ZnSO4) on yield, contents of total phenolic, total flavonoids, carotenoids and their antioxidant capacities of the rat-tailed radish (Raphanus sativus var. caudatus Alef), dill (Anethum graveolens L.) and hairy basil (Ocimum africanum Lour.) microgreens was investigated. ZnSO4 at the concentrations of 0, 0.5, 1.0, 1.5, 2.0 and 2.5 µM were sprayed daily during 2 to 11 days after sowing, and microgreens were harvested at the 12th day. The results indicated that high ZnSO4 concentration reduced fresh and dry weight of these microgreens. However, the highest contents of total phenolic and total flavonoids were obtained from 2.5 µM ZnSO4 treatment. The rat-tailed radish and dill microgreens under 1.5 µM ZnSO4 application contained the highest values of DPPH and ABTS free radical scavenging activities, whereas, 1.0 µM ZnSO4 enhanced the highest values of both antioxidant capacities in hairy basil microgreen. In addition, lycopene and b-carotene contents in vegetable microgreens showed significant response to levels of ZnSO4 Based on these results, sulphur fertilisation with ZnSO4 has potential to enhance the antioxidant contents, carotenoids and their activities of these indigenous vegetable microgreens.
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