UV-B Driven Metabolite Enrichment and Functional Bioactivity Enhancement in Allium cepa L.

IJEP 46(11): 1065-1075 : Vol. 46 Issue 11 (November 2026)

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Pasupath Y Allasamy1, Shanthi Natarajan1* and Murugesan Subbiah2

1. Pachaiyappa’s College (Affiliated to University of Madras), P.G. and Research Department of Botany, Unit of Plant Stress Physiology, Chennai – 600 300, Tamil Nadu, India
2. Pachaiyappa’s College, P.G. and Research Department of Botany, Unit of Algal Biotechnology and Bionano- technology, Chennai – 600 030, Tamil Nadu, India

Abstract

This research examines the morphological, biochemical, phytochemical and proteomic responses of onion (Allium cepa L.) to ultraviolet-B (UV-B) radiation. In particular, UV-B-exposed plants showed greater morphological improvements, reflected in greater shoot extension, increased leaf count, increased bulb size and improved root structure, which are attributed to increased vigor and adaptive growth under UV-B stress. Biochemical testing showed increased chlorophyll, carotenoids, flavonoids and anthocyanins relative to controls, indicating UV-B-mediated stimulation of pigment biosynthesis and accumulation of secondary metabolites. High-performance liquid chromatography (HPLC) results showed an increase in water-soluble vitamins (C and B-complex) following UV-B irradiation and a decrease in fat-soluble vitamins (A, D, E and K), suggesting selective photostability under stress and metabolically regulated behaviour. Phytochemical analysis showed moderate increases in phenolic, flavonoid and alkaloid levels, consistent with activation of the phenylpropanoid pathway. Antimicrobial assays showed greater effectiveness against Bacillus pumilus and Candida albicans because of the increased levels of phenolic and flavonoid compounds. The SDS-PAGE analysis of chloroplast proteins showed that UV-B-treated plants produced stronger bands at ~35, ~45 and ~55 kDa, corresponding to proteins that help plants respond to stress and protect themselves from UV damage. The research results showed that moderate UV-B exposure helps onions develop better physical strength, increase pigment production and vitamin levels and enhance antimicrobial defense through biochemical and proteomic changes, demonstrating their ability to adapt and remain healthy.

Keywords

Allium cepa, UV-B radiation, morphological adaptation, secondary metabolites, chloroplast proteins, phenyl propanoid pathway, antimicrobial activity

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