Integrated biochemical and hormonal reprogramming of Aronia melanocarpa under deficit and surplus irrigation: modulatory roles of osmoprotectants

Abstract Background Irrigation extremes, including both water deficit and excessive water supply, can markedly alter plant metabolism. However, the integrated biochemical and hormonal response of aronia ( Aronia melanocarpa ) to contrasting irrigation regimes remains poorly understood. This study aimed to investigate how different irrigation levels, ranging from severe deficit to surplus irrigation, interact with osmoprotectant applications to regulate oxidative stress, osmotic adjustment, antioxidant defense, and hormonal balance. Methods This study evaluated the impact of six irrigation treatments at field capacities of 20%, 40%, 60%, 80%, 100%, and 120% FC, in conjunction with foliar sprays of individual osmoprotectants: proline (10 mM), glycine betaine (50 mM), and trehalose (20 mM), each administered independently. The resulting dataset was evaluated using a comprehensive statistical approach, including preliminary variable screening, two-way ANOVA, heatmap analysis, principal component analysis (PCA), and Pearson correlation analysis to identify key metabolic and hormonal markers, particularly malondialdehyde (MDA), hydrogen peroxide (H2O2), proline, soluble sugars (glucose, fructose, sucrose), and essential phytohormones, including abscisic acid (ABA), indole-3-acetic acid (IAA), jasmonic acid (JA), and zeatin. Results Irrigation level emerged as the dominant factor structuring the biochemical and hormonal response, with the strongest analytical signals concentrated in redox-related compounds, soluble sugars, selected amino and organic acids, and hormones. While irrigation was the primary driver, osmoprotectant treatments exerted selective and context-dependent effects; trehalose and glycine betaine were the most efficient in alleviating water deficit through enhanced sugar-based osmotic buffering, whereas exogenous proline (10 mM) triggered localized phytotoxicity by amplifying oxidative load under surplus irrigation (120% FC). Multivariate analyses revealed that oxidative stress markers, osmolytes, and antioxidant enzymes formed distinct but interconnected response modules across treatment combinations, governed by coordinated interactions among redox regulation and hormonal signaling. Conclusions Aronia melanocarpa exhibits a highly structured biochemical response to both insufficient and excessive irrigation, and osmoprotectant applications modulate this response in a treatment-specific manner. These findings provide an integrated framework for understanding irrigation-dependent stress physiology in aronia and support the development of more precise water and stress management strategies.