The study investigates the use of silver nanoparticles (AgNPs) in agriculture, focusing on their potential to enhance the immune response of potato (Solanum tuberosum L.) plants against phytopathogenic attacks. The research highlights how AgNPs, stabilized by biologically active polymers polyhexamethylene biguanide and tallow amphopolycarboxyglycinate, can induce oxidative stress. Triple foliar application of 0.1–9.0 g/ha silver nanoparticles at the budding and later stages demonstrated significant efficacy in suppressing diseases caused by Phytophthora infestans and Alternaria solani (over 60%). This effect was linked to the increased activity of peroxidase—over 30–50%—and the decreased catalase activity, indicative of a well-coordinated oxidative stress response to the invasion of P. infestans and A. solani. The results suggest that AgNPs in low concentrations can prime the plant’s innate immune system, enhancing its resistance without detrimental effects on growth parameters, thus contributing to the improved crop yield. These findings underscore the potential of AgNPs not as traditional biocides, but as intelligent elicitors of plant-induced resistance, positioning them as next-generation tools for sustainable crop protection and yield optimization, which can be applied at extremely low doses (less than 10 g/ha of active substance).

The study evaluated the potential of low-dose foliar melatonin (MT) treatments to alleviate chilling injury in cucumber plants, with a particular focus on mimicking sudden spring frosts in open-field cultivation. Cucumber seedlings were sprayed with MT solutions at 0.1, 1, and 10 mg L⁻¹ (0.4, 4, 40 µM respectively), then subjected to a controlled chilling regime (4 °C for 72 h). A set of biochemical and physiological parameters was assessed, including stem elongation, leaf area, tissue water content, photosynthetic pigment concentrations, malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) accumulation, antioxidant enzyme activities, and soluble carbohydrate profiles. In addition, the thermostable fraction of chlorophylls a and b was determined as an indicator of photosynthetic system integrity; this parameter substantially increased under MT treatment, particularly at 1 and 10 mg L⁻¹, despite an overall reduction in total pigment content. The results demonstrated that MT pretreatment, especially at 1 mg L⁻¹, significantly mitigated chilling-induced growth inhibition, preserved chloroplast integrity, and reduced membrane lipid peroxidation. Moreover, MT promoted the accumulation of osmo- and cryoprotective sugars, contributing to improved cellular homeostasis under low temperature. These key findings indicate that low-dose MT priming is a promising, nature-derived strategy to enhance the tolerance of cucumber to acute chilling events, supporting the development of sustainable and organic-friendly approaches for spring frost protection.