Improving drought tolerance in some wheat genotypes with foliar application of silicon nanoparticles in Al-Dawadmi, Saudi Arabia

Water stress, even at light or moderate levels, can negatively affect wheat physiology by altering gas exchange and photosynthetic pigments, thereby restricting growth, while severe stress further amplifies these effects and leads to more pronounced yield reductions. Foliar application of silicon nanoparticles (SiNPs) may help mitigate some of these detrimental effects on wheat's physiological and agronomic traits, as evaluated over two growing seasons at a single location. To test this hypothesis, two field experiments were conducted during the 2022/2023 and 2023/2024 winter seasons at the Experimental Farm in Al-Dawadmi, Saudi Arabia. The study evaluated the response of eight wheat genotypes to foliar-applied SiNPs under three irrigation regimes representing full, moderate, and severe water stress conditions. Agronomic and physiological characteristics of wheat were negatively affected by moderate and severe water stress. In comparison to the untreated control, the application of 100 and 200 mg L^-1 of SiNPs, particularly at the higher concentration, alleviated some of the negative effects of water stress on various physiological and yield traits, with Giza 171, SOKOLL, and Giza 168 showing the most pronounced improvements. In the same context, under severe water stress, SiNP application improved net photosynthesis (up to 57.19%), transpiration rate (up to 36.20%), stomatal conductance (up to 31.34%), intercellular CO₂ concentration (up to 34.21%), water use efficiency (up to 15.69%), relative water content (up to 38.16%), chlorophyll content (up to 37.51%), spikes per plant (up to 50.80%), grains per spike (up to 56.52%), and grain yield per hectare (up to 50.33%). These results demonstrate the potential of SiNP application to improve drought tolerance in wheat genotypes under the specific agro-ecological conditions of Al-Dawadmi and highlight genotype-specific responses, particularly in Giza 171 and SOKOLL. While confirming previous findings on the role of silicon in mitigating drought stress, this study provides novel insights into the differential responses of wheat genotypes in an arid environment. However, further multi-location and long-term trials are needed to validate these effects and to assess environmental safety, soil accumulation, and practical feasibility.