LAUSR

Abstract Species in the Cupressaceae have high potential phytotoxic effects leading to various perturbations of growth, physiological and biochemical processes in weed plants. A study was conducted to evaluate the effect of aqueous leaf extracts of Cupressus sempervirens L., Juniperus phoenicea L. and Tetraclinis articulata (Vahl) Mast. on the physiological and biochemical processes in Lactuca sativa L. (lettuce) Results showed that the application of these aqueous extracts at concentration corresponding to IC50 (50%) inhibited root growth, caused great phytotoxicity in lettuce, including necrosis and morphological modifications, triggering oxidative damage, disruption in membrane permeability showing strong electrolyte leakage, lipid peroxidation as was evidenced by increased content of malondialdehyde and disturbance of mitochondrial respiration. Both chlorophyll a and chlorophyll b were significantly reduced while carotenoid content increased. Proline content was also increased in the treated plants by these extracts. The increase of the production of secondary metabolites with antioxidant potential especially for the roots was the result of the lyase enzyme activity stimulation. The importance of these phenomena varied with the test extracts, reflecting their differential chemical compositions. Impairment of various metabolic activities due to the application of these aqueous extracts resulted in decreased root and shoot length.