ZnSO₄ spraying affects the growth and phytochemicals of Chinese kale microgreens

Abstract

Chinese kale microgreens are gaining interest for its phytochemical compounds and anti-cancer properties mainly from glucosinolates. Zinc is an essential for plant growth and is involved with phytochemicals accumulation. This study investigated the different concentration of ZnSO₄ on the enhancement of the phytochemicals and quality of Chinese kale microgreens. Three-day-old seedlings were sprayed with 2 and 4 mM of ZnSO₄ until harvesting on days 4, 5, 6 and 7. ZnSO₄ significantly decreased the fresh weight of 6 and 7-day-old microgreens and dry weight on the 7^th day. The total glucosinolates, total phenolic compounds and total ascorbic acid, gradually rose as the age of microgreens increased. When the 3-day-old microgreens were sprayed at 6, 12 and 18 mM, the fresh and dry weight and hypocotyl length of 7-day-old microgreens significantly decreased as the concentration increases. ZnSO₄ at 18 mM was the most effective in enhancing phytochemicals, resulting in increased DPPH radical scavenging activity and ferric reducing antioxidant power. This concentration also induced phenylalanine ammonia lyase activity resulting to an increase in total phenolic compounds. Moreover, ZnSO₄ at 18 mM induced H₂O₂ content but are sufficiently countered with the increase in antioxidant enzymes namely superoxide dismutase, catalase, and ascorbate peroxidase. In conclusion, the 3-day-old microgreen was the most effective age for the start of the daily spraying of ZnSO₄ before harvesting at 7-day-old. Higher concentrations of ZnSO₄ (6-18 mM) enhanced the phytochemical compounds and enzymatic antioxidant activities but reduced growth. In contrast, lower concentration (< 4 mM) only improved microgreens growth.

Keywords:

• Antioxidant enzymes
• Chinese kale microgreens
• plant growth
• phytochemical compounds
• zinc sulfate (ZnSO₄)

Acknowledgments

The authors thank to The United Graduate School of Agricultural Science (UGSAS), Gifu University, Japan for supporting some equipment in this study.

Disclosure statement

No potential conflict of interest was reported by the authors.

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

This research was supported by the Petchra Pra Jom Klao Ph.D. Research Scholarship from King Mongkut’s University of Technology Thonburi.