Red and blue light-emitting diodes accelerate 2,4-D phytoremediation by <i>Plenctranthus neochilus Schltr</i>. and assist in homeostasis via antioxidant defense mechanisms

The herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) is highly toxic and has the potential to contaminate water resources and affect non-target organisms. <i>Plectranthus neochilus</i> is capable of phytoremediating this herbicide, although the process occurs at a slow rate, possibly as a result of the compounds’s toxicity. To reduce this effect, the use of red and blue light-emitting diodes (LED) proved to be efficient, stimulating enzymatic and non-enzymatic antioxidant mechanisms that minimize oxidative stress and improve phytoremediation. Therefore, this study aimed to accelerate the phytoremediation of 2,4-D using photostimulation with blue and red LED, analyzing the enzymatic antioxidant and secondary metabolic mechanisms. For this, reproduction by cuttings was employed, and <i>P. neochilus</i> seedlings were divided into three groups: control with water, phytoremediation of water contaminated with 2,4-D and pesticide control. The treatments were conducted under blue and red LED and ambient light. The results show that red and blue LEDs reduced 2,4-D levels by ∼50% and ∼70%, respectively, without the formation of the toxic metabolite 2,4-dichlorophenol. Red light stimulated antioxidant enzymes, including catalase (CAT), superoxide dismutase (SOD), and glutathione S-transferase (GST), while blue LED primarily increased total phenolics and antioxidant activity in leaves, in both cases promoting the preservation of photosynthetic pigments. As a result, photostimulation with red and blue LEDs represents a sustainable and efficient alternative to enhance the decontamination of water resources contaminated with 2,4-D. These findings provide a basis for future investigations and applications in techniques that use light manipulation in the phytoremediation of contaminated waters.