The effects of Silica nanoparticles (SiNPs) application on maize (Zea mays L) growth, defense system and cadmium accumulation under Drought and Cadmium Stress

Background and aims Abiotic stresses, particularly drought and cadmium (Cd) stress, are among the primary limiting factors for global crop production, significantly threatening the growth and development of maize. Silicon nanoparticles (SiNPs) have demonstrated substantial potential in enhancing crop resilience. However, the regulatory mechanisms of SiNPs under combined drought and Cd stress conditions remain insufficiently explored. Methods The experiment included eight treatments: control [100% field capacity (FC), 0 mg/kg Cd)], drought (50% FC, 0 mg/kg Cd), Cd stress (100% FC, 5 mg/kg Cd), combined stress (50% FC, 5 mg/kg Cd ) and each of these with or without SiNPs application (0 or 50 mg/kg). Results Drought and combined drought-Cd stress remarkably reduced maize photosynthetic efficiency, root traits, and grain yield. Cd stress alone had minimal impact on growth parameters but significantly increased Cd accumulation in plant tissues. However, SiNPs application significantly improved root morphology, increased leaf relative water content (LRWC), enhanced antioxidant enzymes activities and increased the contents of soluble sugars and soluble proteins. These changes reduced reactive oxygen species (ROS) and malondialdehyde (MDA) levels, thereby promoting photosynthetic efficiency and ultimately increasing grain yield by 27.3% and 18.9% under drought stress and combined stress compared to the non-Si treated plants. Additionally, SiNPs application significantly decreased Cd concentration in plant tissues by reducing Cd bioavailability in soil under Cd stress. Conclusion SiNPs is an effective strategy to mitigate drought stress and Cd accumulation in maize.