Mitigation of alkaline stress and iron deficiency in Petunia hybrida through resveratrol-induced physiological and nutrient responses

Soil alkalinity is a major abiotic stress limiting plant growth and nutrient uptake, particularly in calcareous soils where iron availability is severely restricted. Although various strategies have been explored to mitigate alkaline stress and iron deficiency in crops, the role of resveratrol—a non-flavonoid polyphenolic phytoalexin known for its potent antioxidant and signaling properties—has not been thoroughly investigated in ornamental species under such stress conditions. This study aimed to evaluate the physiological, biochemical and nutrient-modulating effects of foliar-applied resveratrol on Petunia hybrida cv. Supercascade Rose subjected to combined alkaline and iron-deficiency stress. A greenhouse factorial experiment was conducted with nutrient solutions at two pH levels (6.0 ± 0.2 and 8.3 ± 0.2) and two iron concentrations (15 and 1.5 mg L⁻¹ Fe), along with three resveratrol treatments (0, 100, and 200 µM) applied biweekly. Under alkaline and low-iron conditions, plant biomass was reduced by approximately 49–52%, total chlorophyll content declined by nearly 80%, and oxidative stress markers including electrolyte leakage, hydrogen peroxide (H₂O₂), glycine betaine (GB), and malondialdehyde (MDA) increased significantly. Resveratrol application, particularly at 100 µM, significantly alleviated these adverse effects by enhancing biomass by 63.5%, increasing chlorophyll content by 148%, and reducing oxidative damage markers by approximately 15%, compared to untreated stressed plants. Furthermore, resveratrol boosted ferric chelate reductase (FCR) activity, promoted macro- and micronutrient accumulation in roots and leaves, and preserved water status and membrane integrity. This study provides the first comprehensive evidence demonstrating that exogenous resveratrol effectively mitigates the detrimental impacts of alkaline and iron-deficiency stresses in an important ornamental species. The findings underscore resveratrol’s potential as an eco-friendly, cost-effective biostimulant to enhance nutrient use efficiency, oxidative stress tolerance, and overall resilience of floricultural crops grown in suboptimal soil environments.