Mitigation of Oxidative Damage Caused by Salinity in the Halophyte Crithmum maritimum L. via Biostimulant-Enhanced Antioxidant Activity

The xerophyte medicinal species <i>Crithmum maritimum</i> was investigated for its physiological and antioxidant responses under increasing salinity stress and foliar biostimulant application. At moderate salinity (10 dS/m sodium chloride NaCl), plant growth and photosynthetic activity were enhanced, whereas high salinity (20 dS/m) led to significant reductions in biomass, photosynthetic efficiency, and water use efficiency. Salinity-induced oxidative stress was confirmed by elevated levels of malondialdehyde (MDA) and hydrogen peroxide (H₂O₂), in upper plant tissues. Foliar application of two bioactive compounds-Aquamin and Cultisano-partially mitigated the detrimental effects of high salinity. Treated plants maintained higher photosynthetic parameters and exhibited improved antioxidant profile compared to untreated controls. Furthermore, GC-MS analysis of essential oils revealed that salinity altered the composition of key volatile components, notably increasing <i>γ</i>-terpinene and reducing <i>p</i>-cymene content. Biostimulant treatments counteracted these changes, enhancing terpene components such as <i>p</i>-cymene, and thymol-methyl-ether. Overall, the findings highlight the potential of biostimulants to enhance both salt tolerance as well as the phytochemical value of <i>C. maritimum</i>, suggesting promising applications in sustainable agriculture and high-value plant product development under saline conditions. It was concluded that the type of biostimulant significantly influenced the physiological and quality characteristics of sea fennel plants. Further study on this topic is proposed, aiming at the improvement of antioxidant activity, which is beneficial to human health.