Introduction: Plant biostimulants are pivotal to developing more sustainable agricultural systems, enhancing crop performance, and reducing reliance on synthetic inputs. Among them, botanical extracts remain underexplored, especially those derived from wild plant species. In this study, Silene inflata, a spontaneous herbaceous plant typical of Mediterranean grasslands, was investigated for its biostimulant potential on lettuce.
Methods: Leaves and roots of S. inflata were collected from greenhouse-grown plants and stored at - 80°C. Both tissues were biochemically characterized for polyphenols, ascorbate, proteins, saponins, chlorophylls, and carotenoids. Aqueous phosphate-buffered extracts from leaves (LES) and roots (RES) were prepared via ultrasound-assisted green extraction. A pilot study showed that irrigation was more effective than foliar spraying, and this method was used in the main experiment. Three-week-old Lactuca sativa L. (cv. Canasta) seedlings were transplanted into 10 cm pots and grown in a greenhouse under natural light (15 h day/9 h night; 7-25 °C). Plants were irrigated daily with 20 mL of tap water. On treatment days, 10 mL of tap water was applied, followed 1 h later by 10 mL of LES or RES at 1 or 10 mL/L once per week for three weeks. Controls received water or PBS.
Seven days after the last treatment, plants were harvested for fresh/dry weight measurements and biochemical analyses.
Results: RES showed high saponin levels, while LES had five times more polyphenols. Ascorbate and soluble proteins were higher in leaves (17 mg/100 g FW and 0.5 mg/g FW, respectively). LES at 10 mL/L significantly improved biomass, while LES at 1 mL/L enhanced chlorophylls, carotenoids, and polyphenols. Protein content was reduced in LES 10-treated plants. Overall, LES had stronger biostimulant effects in a dose-dependent manner. Additionally, S. inflata was successfully cultured in vitro, suggesting its suitability for sustainable biomass production.
Conclusions: These findings reveal S. inflata as a promising biostimulant, highlighting the value of wild plant biodiversity for sustainable agricultural innovation.
