Mechanistic insights into the role of chitosan nanoparticles in enhancing plant drought tolerance

Abstract Enhancing crop drought resilience is a critical goal for sustainable agriculture under increasing climate variability. Chitosan nanoparticles (ChNPs) have emerged as effective biostimulants; however, their drought-mitigating action remains insufficiently defined at the mechanistic level. Here, we synthesize current evidence to propose a causal mechanistic framework linking ChNP input characteristics (particle size∼20–200 nm; application doses typically 30–400 ppm) to plant physiological and molecular responses under drought stress. Following root or foliar uptake, ChNPs are translocated through apoplastic and symplastic pathways, enabling interaction with photosynthetic and stress-responsive tissues. This uptake initiates signaling cascades involving controlled reactive oxygen species (ROS) modulation and abscisic acid (ABA)-related pathways. Evidence from multiple controlled studies, primarily in leaf and root tissues under moderate drought conditions, indicates that ChNP application is associated with the upregulation of key drought-responsive genes, including LeNCED1 (ABA biosynthesis) and SlAREB1 (an ABA-dependent transcription factor), typically showing modest but consistent induction compared with untreated drought-stressed plants. These molecular responses translate into improved photosynthetic efficiency, enhanced osmolyte accumulation, and stronger antioxidant defenses, collectively reducing oxidative damage and improving drought tolerance. While these findings highlight the mechanistic potential of ChNPs, careful dose optimization and environmental assessment remain essential for sustainable agricultural application.