The synergistic effects of phenylalanine and biochar to ameliorate cadmium (Cd) stress and restoring the morpho-physiological traits of maize (Zea mays) in Cd-contaminated agricultural soil.

Cadmium (Cd) negatively impacts plant health in ecosystems. Biochar (BC) can remediate excessive Cd accumulation in plants, and phenylalanine (Phe) enhances plant antioxidant capabilities under stress. However, the combined effects of Phe and BC on Cd toxicity in maize are not fully understood. Therefore, a controlled environment study was conducted to assess the impact of both individual and combined applications of Phe (100 mg L) and BC (5 % w/w) on morphophysiological traits of maize cultivated in soil contaminated with 30 ppm of Cd. It was observed that high Cd levels decreased various agronomic traits, including root length, root dry biomass, root fresh biomass, shoot length, shoot dry biomass, shoot fresh biomass, and leaf area, in maize compared to the control plants. Notably, both individual and combined treatments of Phe and BC significantly improved the physiological and morphological characteristics, antioxidant capacity, and photosynthetic efficiency of maize cultivated in soil contaminated with Cd. Particularly, the synergistic application of Phe and BC reduced Cd levels in the leaves, shoots, and roots of maize by 84.8 %, 59.6 %, and 63.7 %, respectively, compared to control plants grown in soil contaminated with Cd. The application of Phe and BC modulated the expression of key genes associated with Cd stress response in maize, including metalloprotease (MT1), superoxide dismutase (SOD), nitrate reductase (NR), Cd-transporting ATPase (CdATPase), DELLA protein, and auxin response factor 12 (ARF), thereby enhancing the plant's physiological resilience under Cd exposure. Overall, current study findings demonstrate that the combined application of Phe and BC is an effective strategy for reducing Cd toxicity and enhancing maize growth in contaminated soils, providing a practical approach for improving crop resilience and food safety in heavy metal-affected agricultural systems.