Silicon Seed Priming Mitigates Drought-Induced Effects on Growth, Water Status, and Photosystem Activity in Maize

Water deficit is a major abiotic constraint limiting maize growth and productivity worldwide. Although silicon (Si) is not classified as an essential element, its beneficial effects on numerous crop species are well documented. Silicon has been shown to promote plant growth and enhance tolerance to abiotic stresses, particularly drought stress. Seed priming, a pre-sowing technique known to stimulate early germination processes, has emerged as a promising approach to enhance seedling establishment and stress tolerance in crops. In the present study, silicon-based seed priming was investigated as a strategy to alleviate the adverse effects of water deficit in maize (Zea mays) using two sodium silicate priming-solution concentrations (10 and 20 mM). Maize plants were subjected to six experimental treatments based on seed priming: three under well-watered conditions (no silicon seed priming and seed priming with 10 and 20 mM sodium silicate solutions) and three corresponding treatments combined with irrigation withdrawal for 15 days to induce drought stress. Morphological traits, biomass accumulation, photosynthetic pigment content, plant water status, and PSI- and PSII-related photochemical parameters were evaluated. Drought stress markedly reduced plant growth, biomass production, relative water content, chlorophyll pigment levels, and photosystem photochemical performance, reflecting a strong negative impact of water deficit on most measured parameters. In particular, root and shoot fresh weights decreased by 75% and 71%, respectively, compared with those of well-watered unprimed control plants, indicating a substantial reduction in biomass accumulation under drought conditions. Furthermore, drought conditions impaired photochemical performance and increased non-regulated energy dissipation, indicative of impaired photosynthetic performance. Silicon seed priming mitigated several drought-induced effects in a trait-dependent manner. Under water-deficit conditions, 20 mM Si produced the strongest improvement in root and shoot fresh weights, whereas 10 mM Si showed stronger responses for selected shoot-growth and PSI-related parameters. Both Si treatments improved leaf water status and photosynthetic stability to varying extents. Collectively, these results indicate that sodium silicate seed priming partially improves drought-related responses in maize seedlings under the conditions of this study by sustaining growth performance, preserving plant water status, and maintaining photosynthetic stability under water-deficit conditions.