Silver nanoparticles priming for drought tolerance in wheat: insights from antioxidant system activation and stress memory

Abstract Background AgNPs (nano-silver), as an important nano-material, has been shown to produce reactive oxygen species (ROS). This feature can be applied to crop production, triggering a slight stress response and improving tolerance to subsequent stresses. This study investigates the effects of AgNPs on the antioxidant system of newly developed wheat leaves, highlighting their potential to enhance crop resilience. Methods The morphology and particle size of AgNPs were observed using a transmission electron microscope (TEM). The effects of AgNPs were evaluated by measuring chlorophyll content and chlorophyll fluorescence. Antioxidant enzyme activities and malondialdehyde content were quantified, and changes in intracellular reactive oxygen species (ROS) were detected using 2’,7’- dichlorofluorescin diacetate (DCFH-DA) probe to investigate the physiological mechanism by which AgNPs enhance wheat drought tolerance. Additionally, silver content in different wheat tissues was determined using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Results Our findings demonstrate that lower concentrations of AgNPs (1 mg·L−1) improve drought tolerance without adversely affecting plant growth, while higher concentrations (5 mg·L−1 and 10 mg·L−1) have detrimental effects. Pre-treatment with 1 mg·L−1 AgNPs primes wheat plants for enhanced drought tolerance by inducing a stress memory effect, likely mediated by reactive oxygen species (ROS) signaling. Spatiotemporal analyses revealed that AgNPs treatment leads to a controlled ROS accumulation, which activates the antioxidant system, reduces lipid peroxidation, and enhances photosynthetic efficiency under drought conditions. Moreover, AgNPs application significantly increases grain yield, with accumulation primarily in leaves and stems and no detectable presence in grains, suggesting a low risk of contamination in the food chain. Conclusions Spraying AgNPs produces ROS, which triggers the wheat stress response and forms stress memory. This enables wheat plants to respond rapidly to subsequent drought stress. AgNPs also enhance antioxidant enzyme activity, reduce lipid peroxidation, mitigate drought-induced damage, maintain photosynthetic efficiency, and ultimately improve wheat yield under drought conditions. Graphical Abstract