Phytochemical Adaptation Strategies of Citrus Plants: Foliar Application of Bio-Stimulants Under Salt Stress

Salinity is one of the major abiotic factors that limits citrus productivity. This research focused on the effects of bio-stimulants derived from Rosmarinus officinalis, Pinus pinea) and shrimp chitin, on the biochemical responses, as well as the adaptive strategies of citrus under salt stress. Photosynthetic pigments, osmolytes such as proline and soluble sugars, nutrition availability, iron rheostats and secondary metabolites were analyzed to determine salt stress tolerance. Our results demonstrated that different bio-stimulant enhances photosynthetic efficiency and increases chlorophyll levels. In addition, the negative impact of salinity on citrus was mitigated by increasing osmoprotectant levels, which play a crucial role in reactive oxygen species (ROS) balance. The present study elucidates the impact of rosemary bio-stimulant which has been found to enhance better salt stress tolerance, increasing levels of soluble sugars to maintain photosynthetic sta-bility. Furthermore, plants treated with Rosemary maintained moderate levels of stress biomarkers, namely proline and carotenoids. To tolerate salt stress, this bio-stimulant helps to optimize soil homeostasis and improves its edaphic properties, by reducing electrical conductivity and stabilizing K+/Na+ ratio. Nevertheless, it maintains the availability of essential nutrients, including sodium, Potassium, Phosphorus and iron. LCMS/MS analysis revealed significant accumulation of defense-related secondary me-tabolites in citrus plants treated with rosemary, including kojic acid and kaempferol. Nevertheless, stressed plants accumulated increased levels of stress-signaling compo-nents and defensive antioxidants, particularly salicylic acid and ferulic acid.