Leaf physio-biochemical traits and antioxidant responses of Malva sylvestris to drought stress

Common mallow (Malva sylvestris) is an important medicinal plant in both traditional and modern medicine. Various parts of this plant, such as the leaves, flowers, roots, and seeds, produce important biological compounds used in conventional medicine and the food industry. Despite its medicinal value, little is known about how its populations respond to drought stress at the physiological and biochemical levels. This research aimed to investigate the diversity and response of M. sylvestris populations to different physio-biochemical traits under drought stress. A field experiment was conducted with 10 populations of M. sylvestris using a randomized complete block design with three replications under normal irrigation up to 80% FC (field capacity) and drought stress 60% FC in the research institute forest and rangeland in Tehran, Iran, in 2023. Leaf samples were collected during the flowering stage, and some physio-biochemical traits and antioxidant activities were measured. Results indicated that drought stress decreased leaf area index (LAI), relative water content (RWC), chlorophyll levels, and stomatal density, while increasing osmolyte content, phenolics, anthocyanins, and antioxidant enzyme activity. These adjustments promoted osmoprotectant accumulation and strengthened antioxidant defenses, indicating an adaptive response to oxidative stress under water deficit. Genotype G9 (code 38767, Shirvan) showed the highest solute accumulation and drought tolerance, making it a promising candidate for breeding drought-resistant cultivars. Further research is recommended to explore the pharmacological properties of its secondary metabolites and to develop drought-resilient cultivars for use in herbal medicine and phytopharmaceuticals industries.