Chitosan nanoparticles and their conjugates in drought stress management: A cutting-edge strategy for crop resilience

Global food security is at risk due to crops being exposed to more and more unexpected environmental factors, such as high temperatures, unpredictable rainfall patterns, and decreasing soil fertility. Among these, drought is one of the most severe abiotic stresses, arising from prolonged precipitation shortfall that upsets the hydrological balance. It causes extensive ecosystem stress and leads to a reduction in maximum fluorescence (Fm) and variable fluorescence (Fv), which is an indicator of drought. Traditional synthetic fertilizers and pesticides exacerbate environmental degradation. Chitosan nanoparticles (CSNPs), derived from the natural polysaccharide, have emerged as a potential stress alleviator as well as a growth promoter that can help plants cope with physiological and biochemical modifications caused by drought stress. Their nanoscale size (10 to 200 nm) improves bioavailability and absorption, enabling more effective interaction with plant cellular systems. CSNPs can promote growth, improve photosynthetic ability, and regulate osmatic and hormonal activities. Moreover, CSNPs can serve as a promising carrier for bioactive compounds such as phytohormones, micronutrients, or signalling molecules to further boost drought tolerance, called as Chitosan Nanoconjugates (CNCs). These CNCs have the potential to activate the antioxidant defence systems (Superoxide Dismutase, Catalase, Peroxidase, Ascorbic acid, Glutathione) in plant cells. They also facilitate the accumulation of osmolytes (like proline, sugars, and polyols), thereby maintaining cellular integrity under stress conditions. By integrating nanotechnology in agriculture, CSNPs and CNCs offer a novel frontier in precision agriculture, enabling targeted and efficient stress mitigation. Their role as growth enhancers and in improving plant resilience underscores their significance as next-generation biomaterials for sustainable crop production. This review highlights the potential role of CSNPs and CNCs as growth promoters and their mechanistic role in mitigating drought stress in plants. The use of chitosan and its nanoconjugates represents an integrated approach for addressing agricultural challenges, particularly stress management by strengthening crop resilience against drought stress. Drought stress impact on plants and chitosan nanoparticles mediated stress mitigation. • Drought stress severely limits plant growth and agricultural productivity. • Chitosan nanoparticles (CSNPs) modulate plant biochemical responses. • Nanoscale size improves bioavailability and cellular uptake in plants. • CSNPs application mitigates the harmful physiological effects of drought. • Nano-biotechnology provides solutions for resilient agroecosystems.