Investigating the synergistic effects of nano-zinc and biochar in mitigating aluminum toxicity in soybeans

Aluminum (Al) toxicity limited root growth by reducing nutrient translocation and promoting reactive oxygen species (ROS) accumulation, particularly in soybean. The endophyte of root could be modified by plant metabolites, which could potentially alter the tolerance to environmental toxicity of plants in acidic-Al soils. To explore how they help soybean mitigate Al toxicity by altering root endophytes, zinc oxide nanoparticles (ZnO NPs) at doses of 0, 30, 60, 90 mg/kg and 2% biochar (BC) were selected as bio modifiers, and Al₂(SO₄)₃ at 19 mg/kg was used to simulate Al toxicity. We analyzed root endophytes and metabolites by high-throughput sequencing and gas chromatography-mass spectrometry (GC-MS). We found that ZnO NPs with BC could bolster soybean resilience against Al toxicity by enriching soil nutrients, activating enzymes, and bolstering antioxidant mechanisms. We also observed that it enriched root endophytic microbial diversity, notably increasing populations of Nakamurella, Aureimonas, Luteimonas, and Sphingomonas. These changes in the endophytes contributed to the improved adaptability of plants to adversity under Al toxicity. This study highlighted the potential of using ZnO NPs and BC as a sustainable approach to combat Al toxicity, emphasizing the intricate interplay between plant physiology and rhizosphere microbial dynamics in mitigating the effects of environmental toxicity.