ZnO-nanoparticles and stage-based drought tolerance in wheat (Triticum aestivum L.): effect on morpho-physiology, nutrients uptake, grain yield and quality.

Drought-stressed and zinc-deficient soils are major contributors to reduced wheat yields and low-quality grains, especially in semi-arid regions of the world. Zinc-oxide nanoparticles (ZnO-NPs) are adept enough to avoid these losses if applied under the right dose at the right growth stage of many crops including wheat (Triticum aestivum L.). Therefore, a pot experiment was conducted with four levels of ZnO-NPs (0, 50, 100 and 150 ppm), and drought imposed at tillering (D) and grain filling (D) stages, considering normal irrigation as control (D), to explore interactive effects of ZnO-NPs and drought episodes on growth, eco-physiology, yield, and grain quality of wheat. The results depicted dose and growth stage-dependent variations in all recorded parameters. ZnO-NPs (150 ppm) significantly increased the number of grains (12.5%), grain weight (12.4%), total yield (25.5%), and zinc contents (58.6%) when the crop was exposed to drought stress at tillering stage, compared to the control treatment. Likewise, drought at grain filling stage with ZnO-NPs (150 ppm) significantly enhanced plant height, spike length, biomass, zinc contents, and grain protein by 15.5%, 3.2%, 16.7%, 100.0%, and 53.8%, respectively, when compared with control treatment. Thus, ZnO-NPs emerged as a potential drought alleviator and yield-oriented safe nano-fertilizer for wheat in semi-arid regions facing irrigation challenges.