Exogenous gallic acid enhances growth, essential oil accumulation, and antioxidant defense of dill under soil moisture deficit

Objective Dill ( Anethum graveolens L.) is a valuable aromatic plant, but its cultivation in Egypt’s sandy reclaimed soils is constrained by rapid soil moisture depletion. This study evaluated the effects of gallic acid (GA) on dill growth and biochemical responses under different moisture regimes. Methods Plants were grown at four field capacity (FC) levels (100, 80, 60, and 40%) and either left untreated or foliar-sprayed with GA (30 mg L⁻¹). Morphological, biochemical and essential oil characteristics were evaluated, and data were analyzed using two-way analysis of variance (ANOVA). Key results GA application improved biomass under full FC, increasing fresh and dry mass by 35.1% and 41.3%, respectively, compared with untreated plants at the same FC level. GA also enhanced essential oil production, with essential oil yield increasing by 70.3% at 60% FC compared with the corresponding untreated plants. At 40% FC, GA increased phenolic and flavonoid contents and DPPH radical-scavenging activity, with DPPH inhibition increasing by 10.7%. GA also promoted the accumulation of proline and antioxidant enzymes under severe moisture deficit. Conclusion Foliar GA application enhanced biomass production, essential oil productivity, and antioxidant capacity in dill under reduced water availability, demonstrating its potential as a biostimulant for improving dill performance under moisture-deficit conditions.