Mitigating heavy metal stress in plants: Combined effects of cold plasma seed treatment and dopamine on the physio-chemical response of fenugreek under chromium toxicity

This study investigated the physiological and biochemical responses of fenugreek ( Trigonella foenum-graecum L.) to dopamine (200 μM) application and seed treatment with atmospheric pressure non-thermal plasma (APNP) under chromium (Cr) stress (300 μM). APNP treatment markedly enhanced the hydrophilic properties of seed surfaces, thereby improving their interfacial affinity for water. Exposure to Cr stress alone led to a reduction in photosynthetic pigments and relative water content (RWC), alongside significant increases in hydrogen peroxide (H₂O₂), malondialdehyde (MDA), and electrolyte leakage (EL). The findings of this study indicated that dopamine and APNP, whether applied individually or in combination, significantly modulated the physico-biochemical responses of fenugreek under Cr stress through the enhancement of the plant’s defense mechanisms. The application of these treatments in Cr-exposed plants increased photosynthetic pigment content, RWC, and antioxidant enzyme activities, as well as the accumulation of sugars, phenolic compounds, and proline. In addition, the activities of ascorbate–glutathione cycle enzymes, including monodehydroascorbate reductase and dehydroascorbate reductase, were enhanced, whereas the levels of H₂O₂, MDA, and EL were reduced. Importantly, the co-application of dopamine and APNP (specifically 4 min + 6 kV) resulted in reductions in root and shoot Cr content of 53% and 58%, respectively, compared with Cr-stressed plants without these elicitors. These findings highlight the potential of integrating APNP and dopamine as an effective strategy for mitigating Cr toxicity in fenugreek.