Silicon nanoparticles (SiNPs) have emerged as multifunctional tools in sustainable agriculture, demonstrating significant efficacy in promoting crop growth and enhancing plant resilience against diverse biotic and abiotic stresses. Although their ability to strengthen antioxidant defense systems and activate systemic immune responses is well documented, the fundamental mechanisms driving these benefits remain unclear. This review synthesizes emerging evidence to propose an innovative paradigm: SiNPs remodel plant redox signaling networks and stress adaptation mechanisms by forming protein coronas through apoplastic protein adsorption. We hypothesize that extracellular SiNPs may elevate apoplastic reactive oxygen species (ROS) levels by adsorbing and inhibiting antioxidant enzymes, thereby enhancing intracellular redox buffering capacity and activating salicylic acid (SA)-dependent defense pathways. Conversely, smaller SiNPs infiltrating symplastic compartments risk oxidative damage due to direct suppression of cytoplasmic antioxidant systems. Additionally, SiNPs may indirectly influence heavy metal transporter activity through redox state regulation and broadly modulate plant physiological functions via transcription factor regulatory networks. Critical knowledge gaps persist regarding the dynamic composition of protein coronas under varying environmental conditions and their transgenerational impacts. By integrating existing mechanisms of SiNPs, this review provides insights and potential strategies for developing novel agrochemicals and stress-resistant crops.

Heavy metal (HM) contamination has emerged as one of the most damaging abiotic stress factors due to their prominent release into the environment through industrialization and urbanization worldwide. The increase in HMs concentration in soil and the environment has invited attention of researchers/environmentalists to minimize its' impact by practicing different techniques such as application of phytohormones, gaseous molecules, metalloids, and essential nutrients etc. Silicon (Si) although not considered as the essential nutrient, has received more attention in the last few decades due to its involvement in the amelioration of wide range of abiotic stress factors. Silicon is the second most abundant element after oxygen on earth, but is relatively lesser available for plants as it is taken up in the form of mono-silicic acid, Si(OH)4. The scattered information on the influence of Si on plant development and abiotic stress adaptation has been published. Moreover, the use of nanoparticles for maintenance of plant functions under limited environmental conditions has gained momentum. The current review, therefore, summarizes the updated information on Si nanoparticles (SiNPs) synthesis, characterization, uptake and transport mechanism, and their effect on plant growth and development, physiological and biochemical processes and molecular mechanisms. The regulatory connect between SiNPs and phytohormones signaling in counteracting the negative impacts of HMs stress has also been discussed.

Drug and food industries employ lupine (Lupinus termis). Saline irrigation water is one of the main obstacles to spread of lupine growing in Egypt's reclamation regions. Productivity of plants grown under salty irrigation water can be improved by using silicon nanoparticles (SiNPs) or functionalized silica nanoparticles (FSiNPs). Lupine plant can be harmed by saline water, especially if it includes sodium chloride; consequently, it was projected that lupine production would fail in Egypt's reclaimed soil, where sodium chloride-containing groundwater is used as the principal irrigation source. In this work, Si types were applied to the leaves of lupine to aid in their response to sodium chloride in to lessen the damaging effects of sodium chloride on them for increasing their output in the recently reclaimed regions. Si types were applied to lupine leaves at 0, 1, 2 mM SiNPs, and 1, 2 mM FSiNPs with fresh or saline water. Obtained results indicated that there were different improvements in the morphological characters, yield and fixed oil content, when SiNPs or FSiNPs were applied to lupine plants that had been exposed to saline water. In this way, SiNPs or FSiNPs adapted to saline water by increasing photosynthetic pigments (chlorophyll a or b and carotenoids), osmolytes (proline, soluble sugars, free amino acids), antioxidant molecules (phe-nols and flavonoids), membrane stability index and antioxidant enzymes (catalase, superoxide dismutase, peroxidase and glutathione reductase), while decreasing the values of hydrogen peroxide, malondialdehyde and electrolyte leakage. However, additions of FSiNPs under saline water performed better than SiNPs x saline water treatments. This study assists farmers in reducing the negative impacts of saline irrigation water on reclaimed fields.