Drought stress is a major limiting factor for wheat cultivation in semi-arid regions, a problem often exacerbated by concurrent soil micronutrient deficiencies. While nanofertilizers can improve nutrient uptake and crop resilience, their specific interactions under defined drought stages are not well documented. This two-year field study assessed the impact of foliar-applied nano-zinc oxide (ZnO) and nano-boric acid (H₃BO₃) on the physiological traits and yield of wheat (Triticum aestivum L. cv. 'Bahooth 22') under different irrigation regimes. The experiment used a split-plot factorial design, with drought stress applied during the stem elongation stage in the main plots and nano-fertilizer treatments (control, nano-Zn, nano-B, and their combination) in the sub-plots. Drought stress markedly decreased plant height, fertile tiller numbers, and overall grain yield. However, applying nanofertilizers alleviated these negative impacts. Under water-limited conditions, the combined application of nano-zinc and nano-boron increased grain yield by roughly 42% compared to the untreated control (from 1563 kg ha⁻¹ to over 2200 kg ha⁻¹). This yield boost was primarily driven by improved spike characteristics, specifically longer spikes and more grains per spike, rather than changes in thousand-grain weight. Additionally, nano-zinc was crucial for maintaining total chlorophyll content, which helped preserve photosynthetic capacity during the water deficit. These results indicate that strategically applying nano-zinc and nano-boron as foliar sprays can stabilize physiological functions and sustain yields, providing a practical nutrient management approach for wheat production in water-scarce environments.
