What question did this study set out to answer?

This research aims to elucidate the organ-specific responses of spinach to amino acid biostimulants during salt stress.

July 29, 2026Open Access

Organ-Specific Some Physiological, Biochemical, and Metabolic Responses of Spinach to Foliar and Soil-Applied Aminosol Under Salt Stress

NTNezahat TurfanKastamonu University ADAdilbek DovletovKastamonu University ÖKÖzkan KayaErzincan Binali Yıldırım University

Key Points

This research aims to elucidate the organ-specific responses of spinach to amino acid biostimulants during salt stress.
Investigated physiological and biochemical parameters in spinach under foliar and soil-applied aminosol treatments.
Analyzed growth metrics, pigment content, antioxidant enzyme activities, and secondary metabolite levels.
Utilized multivariate analyses to differentiate treatment groups and assess stress mitigation effectiveness.
Soil-applied aminosol significantly improved antioxidant enzymes and growth parameters compared to foliar application (p ≤ 0.05).
Higher accumulation of antioxidants and better ionic homeostasis were observed with soil application, with reduced Na levels and favorable ionic ratios across tissues.
Distinctive patterns of enzyme activity indicated compartmentalized defense mechanisms in roots and leaves.

Abstract

Abstract Elucidating the organ-specific physiological and biochemical responses of spinach to amino acid-based biostimulants under salt stress is essential for developing sustainable strategies in salt-affected agricultural systems. However, comprehensive knowledge about how different application modes mediate these responses across root, petiole, and leaf tissues remains limited. We investigated growth parameters, pigment contents, oxidative stress markers, antioxidant enzyme activities, mineral nutrition, ionic ratios, phenolic compounds, flavonoids, and antioxidant capacity of Anlani F1 spinach under foliar and soil-applied aminosol and NaCl stress conditions. Application mode and treatment significantly influenced all measured parameters ( p ≤ 0.05). Soil-applied aminosol consistently demonstrated superior stress mitigation, maintaining higher photosynthetic pigment levels, better growth performance, stronger antioxidant defenses, and more effective osmoregulation through enhanced proline accumulation compared to foliar application. Ionic homeostasis was also more effectively restored by soil-applied aminosol, with greater reductions in Na accumulation and more favorable Na/K and Na/Ca ratios across all tissues. Secondary metabolite responses differed markedly between application modes, with soil-applied aminosol producing higher accumulation of quercetin, catechin, total phenolic and flavonoid contents, and greater DPPH radical scavenging activity, consistent with up-regulation of the phenylpropanoid biosynthetic pathway. Antioxidant enzyme distribution revealed a distinct tissue-specific pattern, with APX, POD, and SOD activities peaking in leaves while CAT activity was predominantly elevated in roots, indicating compartmentalized defense regulation. Multivariate analyses including PCA and hierarchical clustering distinguished NaCl-stressed groups from aminosol-treated clusters, indicating a marked shift in the overall physiological and biochemical profile. We conclude that application mode significantly influences aminosol efficacy in mitigating salt stress, with soil application emerging as the superior strategy for enhancing spinach resilience under saline conditions. Differential organ-specific responses provide insights for optimizing biostimulant application protocols, while the quantitative stress response patterns identified offer valuable parameters for improving spinach productivity in salt-affected cultivation systems.

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