In this work, we assessed the impacts of biostimulant application on pot-grown Sonchus oleraceus L. plants under saline conditions. The biostimulant products tested were an experimental formulation based on humic and fulvic acids (HF) and the commercial product Sipfol Star® (SS), which comprises amino acids (mainly glutamic acid, alanine, and aspartic acid). Our results highlight that biostimulants mitigated the negative impacts of high salinity only on specific morphological traits, such as the dry matter of leaves. Accordingly, the HF treatment reduced the fat and protein content (under low and high salinity, respectively) and energetic value (under high salinity), while the carbohydrate content increased under high salinity for the SS treatment and the untreated plants compared to the respective treatment under low salinity. The nitrogen content of leaves was negatively affected by biostimulant application at high salinity, whereas the HF and SS treatments induced the accumulation of sodium and potassium under high salinity compared to the untreated plants. The total flavonoid content also increased in biostimulant-treated plants under high salinity, whereas no effects on total phenol content were recorded. Moreover, the plants treated with biostimulants under low salinity conditions showed higher antioxidant activity for the ferric reducing antioxidant power (FRAP) assay than the respective treatments at high salinity and the control treatment. The content of oxidative markers, such as malondialdehyde (MDA) and hydrogen peroxide (H2O2), was higher under low-salinity levels, whereas biostimulant-treated plants showed the lowest content under high salinity. Overall, the application of biostimulants showed promising results in mitigating the adverse impacts of high salinity on S. oleraceus plants. However, further research is needed on more biostimulatory products and application regimes (e.g., different doses and application times) to elucidate the mechanisms of action and bolster the positive effects of this sustainable agronomic tool.
Polyzos et al. (2026) studied this question.