Chemical Profile and Allelopathic Potential of <i>Ambrosia artemisiifolia</i> Root Exudate

This study investigated the chemical profile and allelopathic potential of Ambrosia artemisiifolia root exudates. Metabolomic profiling was performed on hydroponic culture exudates using XAD-4 resin and UHPLC-QTOF/MS. The analysis identified a total of 1408 metabolites, with stearidonic acid (SA) being the most abundant, accounting for 28.02% of the total root exudate constituents. The allelopathic bioassays conducted on dicot and monocot weed species revealed no statistically significant increase in growth at concentrations of 10-50 µg/mL, whereas inhibition occurred at 250 µg/mL or higher. Monocots exhibited greater sensitivity to the allelopathic effects. At a concentration 500 µg/mL, the application of exudates resulted in a reduction of root and shoot lengths in Setaria viridis by 24.18% and 51.85%, respectively, and in Poa annua by 28.34% and 27.89%, respectively. SA exhibited a stronger inhibitory effect, suppressing root elongation by 43.37% and 71.66% and shoot growth by 33.51% and 64.42% in S. viridis and P. annua, respectively. Moreover, both SA and root exudates modulated superoxide dismutase (SOD) and peroxidase (POD) activities in Amaranthus retroflexus and S. viridis. At higher concentrations, growth was inhibited despite the upregulation of these antioxidant enzymes, suggesting that the accumulation of reactive oxygen species (ROS) exceeded the plants' antioxidant capacity. Results demonstrate root exudates drive invasion by disrupting antioxidant defenses, offering potential for concentration-dependent bioherbicides in sustainable weed management.