Effects of seed priming on growth, nutrient uptake, and biochemical responses of Astragalus fasciculifolius Boiss under drought stress

Astragalus fasciculifolius Boiss ( Astragalus ) is an important medicinal plant whose growth and development are negatively influenced by drought stress. To examine the potential of seed priming in inducing drought tolerance in A. fasciculifolius , a factorial experiment with four replications was conducted in a completely randomized design within a research greenhouse at Torbat Heydarieh University, Iran, in 2024. The experimental treatments were two drought stress levels (no stress: irrigation at 90 % of field capacity (FC), and drought stress: irrigation at 50 % of FC) and eight seed priming treatments including no priming (control), hydropriming (HP), priming with gibberellin (GA 3 ), salicylic acid (SA), potassium nitrate (KNO 3 ), zinc sulfate (ZnSO 4 ), humic acid (HA), and silicon dioxide nanoparticles (SiO 2 -NPs). The results illustrated that drought stress significantly reduced the growth parameters and macro-elements absorption in A. fasciculifolius . However, seed priming with GA₃, ZnSO₄, and HA could moderate the adverse effects of water deficit, leading to significant improvements in plant height, aboveground biomass, and root nutrient uptake (N, P, K). This was associated with increased carotenoid and chlorophyll (Chl) levels. Seed priming with KNO 3 or SA did not significantly differ from the control treatment in terms of growth, physiological and biochemical parameters. The SiO₂-NPs treatment not only failed to induce drought stress tolerance in A. fasciculifolius , but also resulted in significantly lower growth parameters compared to the control. Essentially, the PCA results clearly demonstrated that seed priming with GA₃, ZnSO₄, and HA effectively mitigated the adverse effects of water deficit on A. fasciculifolius production, possibly through enhanced macro-nutrients uptake and increased photosynthetic pigment content.