Differential Cadmium Responses in Two Salvia Species: Implications for Tolerance and Ecotoxicity

Heavy metal contamination poses critical challenges for the cultivation of medicinal plants. This study explores cadmium (Cd)-induced morpho-physiological and metabolic responses in Salvia officinalis (So) and the rare endemic Salvia ceratophylloides (Sc). Plants were exposed to cadmium contamination corresponding to 5 and 10 mg kg−1 Cd (100% and 200% of the Italian regulatory limit) and assessed through gas exchange, leaf anatomy, mineral profiling, polyphenol composition, antioxidant activity, and a preliminary ecotoxicological evaluation using the Artemia salina lethality bioassay. Cd predominantly accumulated in roots, reflecting a partial exclusion strategy, and caused alterations in leaf traits, water relations, and nutrient balance. While total polyphenols generally declined, species-specific responses emerged: S. ceratophylloides increased caffeic acid derivatives, whereas S. officinalis accumulated caffeic acid, lithospermic acid A, quercetin 3-O-glucuronide, and apigenin-O-pentoside at the highest Cd exposure. Polyphenol shifts were strongly associated with antioxidant capacity. Despite higher growth sensitivity, S. ceratophylloides extracts exhibited no toxicity in the A. salina assay, indicating effective metal sequestration and low bioavailability, whereas S. officinalis extracts induced moderate to high toxicity. These findings reveal contrasting Cd tolerance and detoxification strategies, highlighting the potential of integrating plant stress physiology with ecotoxicological assessment and phytostabilization approaches to safely cultivate medicinal species on contaminated soils.