Drought Stress Mitigation in Wheat Seedlings via Green-Synthesized Silver Nanoparticle Priming

Drought is a major abiotic stress that compromises seed germination, seedling establishment, and subsequent crop productivity, thereby threatening agricultural sustainability and food security. Developing effective seed-based strategies is therefore essential to enhance drought resilience. In this study, we investigated the efficacy of green-synthesized silver nanoparticles (AgNPs), produced using Azadirachta indica (neem) flower extract as a seed priming agent, to improve drought tolerance and early growth in wheat (Triticum aestivum). Seeds were primed with AgNPs (25–100 mg L−1), PEG 6000 (−0.6, −0.8, and −1.0 MPa), and their combination (AgNPs + PEG 6000). AgNP priming enhanced germination by 72%, 86%, and 100% at 25, 50, and 75 mg L−1, respectively, compared with the control, with 75 mg L−1 identified as the optimal concentration. This treatment increased total chlorophyll and carotenoid contents by 14% and 6%, and elevated phenolic and flavonoid accumulation by 58% and 97%, respectively. Antioxidant enzyme activities were also substantially increased—catalase (CAT) by 44%, superoxide dismutase (SOD) by 23%, peroxidase (POX) by 11%, and glutathione reductase (GR) by 58%. Under drought stress, AgNP priming at 75 mg L−1 improved germination by up to 80%, indicating enhanced drought tolerance. Elevated protein and antioxidant enzyme levels, along with reduced malondialdehyde (MDA), proline, and total soluble sugar levels, further confirmed mitigation of oxidative stress. Collectively, these results demonstrate that neem-mediated green-synthesized AgNPs could serve as an effective seed-priming agent, promoting wheat seedling establishment and enhancing drought resilience under water-deficit conditions.