Combined herbicidal effects of Cynara scolymus and Papaver rhoeas on weed control through phytochemical analysis

A two-year field trial was conducted to evaluate the phytotoxic potential and physiological effects of artichoke (Cynara cardunculus var. scolymus L.) leaf and common poppy (Papaver rhoeas L.) fruit extracts against the broadleaf weeds, Chrozophora tinctoria L. and Amaranthus retroflexus L. A completely randomized design with three replications was used to test various concentrations (0, 25, 50, and 75 g L^-1) of each extract, both individually and in combination, alongside control treatments including glyphosate. The concurrent objective was to identify allelochemical compounds within the extracts to assess their potential for developing natural herbicide formulations. High-performance liquid chromatography (HPLC) analysis confirmed the extracts possess a high concentration of phenolic and alkaloid constituents. Among the phenolic compounds identified, chlorogenic acid (from artichoke, 1.84 mg g^-1) and rutin (from anemone, 0.48 mg g^-1) were quantified, both possessing documented herbicidal activity. The results indicated that the highest inhibitory potential and herbicidal activity were achieved from the combination of ethanolic extracts of P25A75 and P75A25. In the first and second years, the treatment of P25A75 exhibited an inhibitory effect of 79.66% and 81.66%, respectively, on the growth of C. tinctoria to the control. The highest inhibition of A. retroflexus growth in two years was recorded at 86.33% with the application of the P25A75 extract. This study demonstrated the potent herbicidal effects of artichoke and poppy extracts. The P25A75 and P75A75 treatments significantly reduced the fresh and dry weight of C. tinctoria and A. retroflexus over two years. These extracts induced severe cellular damage, evidenced by a 5- to sixfold increase in electrolyte leakage and a reduction in stomatal conductance of up to 89%. The mechanism involves disruption of Photosystem II and the electron transport chain, leading to chlorophyll degradation. The P25A75 extract exhibited efficacy comparable to glyphosate, highlighting its potential as an eco-friendly bioherbicide.