Seasonal Dynamics of Proline, Soluble Sugars and Flavonoids in Atriplex Halimus L. Across Semi-Arid Regions

Abstract Atriplex halimus L. is a halophytic species widely recognized for its adaptability to harsh environmental conditions, particularly salinity and drought. This study aimed to evaluate the physiological and biochemical responses of A. halimus to seasonal and regional environmental variations in three semi-arid regions of Algeria (Djelfa, Boussaâda, and Tiaret). Leaf samples were collected across four seasons, and key biochemical parameters associated with stress tolerance were analyzed, including proline, soluble sugars, and flavonoids. Proline content was determined using the ninhydrin-based colorimetric method, soluble sugars were quantified following the Dubois method, and flavonoids were measured using the Djeridane method with quercetin as a standard. The results revealed significant seasonal and regional variations in all measured parameters. The highest proline accumulation was recorded during summer, particularly in the Tiaret region (1.475 µg/g DM), consistent with enhanced osmotic adjustment during the hot, dry season. Soluble sugar content also showed elevated levels during summer and autumn, suggesting their role in cellular protection and osmotic balance. Flavonoid concentrations were generally higher during the autumn season, with the highest value observed in Djelfa (3.703 mg/g), suggesting a possible involvement in antioxidative defense mechanisms. Overall, the findings suggest that the accumulation of proline, soluble sugars, and flavonoids may represent adaptive responses enabling A. halimus to tolerate seasonal and environmental stresses. This study provides a comparative seasonal assessment of osmolyte and flavonoid responses of Atriplex halimus across multiple semi-arid regions of Algeria, and these biochemical responses may serve as indicators of plant adaptation to arid and semi-arid ecosystems.