Morphophysiological and phytochemical responses to Arsenic, cadmium and lead stress in Parsley (Petroselinum crispum)

Background This study investigated the effects of varying concentrations of arsenic (As), cadmium (Cd), and lead (Pb) on the morphological, physiological, biochemical traits, essential oil yield and composition, phenolic content, antioxidant activity, and vitamin C content of parsley (Petroselinum crispum). Results Heavy metals exposure significantly reduced plant height, leaf area, shoot biomass, and relative leaf water content, while petiole length, stem diameter, root length, and root biomass increased. Leaf accumulation of As, Cd, and Pb rose proportionally with treatment levels. Photosynthetic pigments (chlorophyll a, chlorophyll b, and carotenoids) and photosystem II efficiency (Fv/Fm) declined significantly, especially under arsenic and lead stress. Despite growth inhibition, essential oil yield increased, peaking at 0.45% (w/w) under 100 mg/kg arsenic. GC analysis identified eighteen oil constituents, with major compounds including apiol, myristicin, β-pinene, and α-pinene. Heavy metal stress reduced oxygenated compounds and increased hydrocarbons in the oil profile. Total phenol and flavonoid contents increased markedly, with the highest values in the 100 mg/kg arsenic treatment (33 mg GAE/g DW phenols and 29 mg QE/g DW flavonoids). Antioxidant assays (DPPH and FRAP) showed enhanced radical scavenging activity and ferric reducing power, with the strongest effects in the As100 and Cd40 treatments. Additionally, vitamin C content significantly increased under heavy metal stress, reaching up to 170 mg/100g fresh weight in the 100 mg/kg arsenic treatment compared to 128 mg/100g in controls. Conclusions These results reveal complex morphological and biochemical adaptations of parsley to heavy metal stress, influencing growth, secondary metabolite production, and antioxidant capacity.