Exogenous jasmonic acid alleviates Cu-induced damages in guinea grass by enhancing photosynthesis, antioxidant enzyme activity and modifying associated metabolites

This study investigated the regulatory mechanism of exogenous Jasmonic acid (JA) in detoxifying Cu stress in guinea grass (<i>Panicum maximum</i>). Seedlings were treated with Cu (300 µM), JA (10 µM), and their combinations <i>via</i> Hoagland solution in controlled growth chambers for 30 days. The results indicated that Cu stress significantly reduced superoxide dismutase (-51.2%) and peroxidase (-38.0%), chlorophyll content, net photosynthetic rate (<i>Pn</i>), and led to decreases in leaf length, width, plant height, and biomass (-49.7%). Conversely, exogenous JA effectively mitigated the adverse effects of Cu stress by reducing membrane damage, and increasing chlorophyll, <i>Pn</i> (+107%), and antioxidant enzymes (<i>p</i><b> </b><<b> </b>0.05), and biomass (+84.7%), modifying associated metabolites. A total of 63 metabolites with differential accumulations were identified when exposed to JA, Cu, or their combination, mainly including amino acids, organic acids, and carbohydrates. Excessive Cu significantly reduced the levels of capric acid, salicylic acid, and glucosaminic acid, while increasing malic acid and serine content, which are primarily involved in regulating the citrate cycle and alanine-aspartate and glutamate metabolism. Overall, these findings demonstrates that guinea grass alleviates Cu toxicity by enhancing photosynthetic efficiency, antioxidant enzyme activity, and modifying associated metabolites and pathways under JA, thereby exhibiting potential for phytoremediation of Cu stress.