Biostimulant-driven growth enhancement and stress resistance in tomato: The combined impact of alginate, chitosan, and salicylic acid.

Mechanical wounding, a significant cause of yield loss in agricultural crops, has prompted recent efforts to identify effective solutions, such as applying biostimulants that not only improve plant growth but also enhance resistance to mechanical damage. This study evaluates the combined effects of alginate (Al-1, 0.75 mg mL-1), salicylic acid (SA, 100 µM), and chitosan (Ch, 0.75 mg mL-1) on tomato plant growth, biochemical responses, and recovery from mechanical wounding. The results indicate that Al-1 accumulates at the plant cell wall, transitioning from a liquid to a film-like state. During this process, Al-1 also loses over 50 % of its sodium ions and fails to acquire nitrogen ions from Ch. However, the combined application of Al-1, SA, and Ch significantly promotes plant growth and enhances mechanical stress resistance by increasing chlorophyll, sugar, protein, and carotenoid levels, as well as improving xylem development compared to other treatments. Furthermore, the Al-1 +Ch+SA combination elevates H2O2 levels and APX activity in adjacent leaves 60 min after wounding; although this response is delayed compared to a individual treatments. These findings suggest that this combination of biostimulants enhances plant resilience to mechanical injury, offering potential for improving crop yield and quality in stress-prone agricultural systems.