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Turkish Journal of Botany

Abstract

Soil salinity is a major abiotic stress affecting over 20% of cultivated and 33% of irrigated lands worldwide, significantly limiting crop productivity and nutrient biosynthesis. Vitamin C and folate are crucial antioxidants in plant stress tolerance and human nutrition; however, their regulation under salt stress remains unclear, particularly in leafy vegetables. This study evaluated the effects of different salinity levels (0, 50, 150, 250, and 350 mM NaCl) on physiological traits, antioxidant activity, vitamin C and folate accumulation, and the expression of related biosynthetic genes in spinach (Spinacia oleracea L.). High salinity (250–350 mM) reduced growth, leaf area, and pigment content, while moderate salinity (50–150 mM) enhanced biomass production and antioxidant activity. Vitamin C content increased 1.99- and 1.75-fold at 50 and 150 mM NaCl, respectively. Total folate levels rose by 17.8% and 13.9%, and free folate by 8.3% and 2.6% under the same treatments. Expression of the VTC2 gene, involved in vitamin C biosynthesis, increased 3.4-fold at 50 mM NaCl. Similarly, five folate biosynthetic genes—GTPCHI, ADCS, DHFS, DHFR, and FPGS—were strongly upregulated under this treatment, but their expression declined at higher salinity levels. Among these, GTPCHI and DHFR showed the highest induction (6.6- and 5.4-fold, respectively), suggesting they serve as key regulatory points in folate biosynthesis under moderate salinity. These results highlight a coordinated physiological and metabolic adjustment that helps sustain spinach nutritional quality under moderate salinity (up to 150 mM NaCl), offering insights into biofortification strategies for saline agriculture, whereas severe salinity suppresses growth and nutrient accumulation.

Author ORCID Identifier

LALEH AHMADI: 0009-0005-1743-4512

HANIEH MOHAJJEL SHOJA: 0000-0003-4752-6600

ELHAM MOHAJEL KAZEMI: 0000-0002-3607-2634

MARYAM KOLAHI: 0000-0002-0212-9719

DOI

10.55730/1300-008X.2899

Keywords

Antioxidant enzymes, folate biosynthesis pathway, salinity stress, spinach, vitamin C biosynthesis

First Page

245

Last Page

259

Publisher

The Scientific and Technological Research Council of Türkiye (TÜBİTAK)

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

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