Changes in Total Phenol and Some Enzymatic and Non-Enzymatic Antioxidant Activities of Rose-scented Geranium (Pelargonium graveolens) in Response to Exogenous Ascorbic Acid and Iron Nutrition

The strong antioxidant activity of Pelargonium graveolens is well established. The question addressed in this study was whether different concentrations of exogenous ascorbic acid (AsA) and iron (Fe) could influence the antioxidant activity and total phenol content (TPC) of geranium. Thus, three levels of Fe (0, 20 and 40 µM) and three levels of AsA (0, 1 and 2 mM) in the nutrient solution were combined factorially based on a completely randomized design with six replications, and chlorophyll content, TPC, and antioxidant activities of the leaves were measured. The results showed that oil content, ascorbate peroxidase (APX), and catalase (CAT) activities were increased in leaf samples under Fe starvation, regardless of the AsA concentration. The highest peroxidase (POD) activity was observed in samples treated with 20 µM Fe and 1 mM AsA. The highest total chlorophyll content was produced in plants treated with 40 µM Fe along with 1 mM AsA. TPC was increased with an increase in Fe concentration. Despite the positive effect of AsA on the pigment contents, plants treated with AsA showed lower TPC under all Fe concentrations. In total, lower Fe nutrition increased oil content and reactive oxygen species (ROS) scavenging activity of geranium. AsA application increased oil content while decreased total phenol and antioxidant activity in this plant.