Enhancing lettuce resilience to cadmium stress: Insights from raw vs. cystamine-modified biochar

Aims and Methods Understanding the interactions among biochar, plants, soils, and microbial communities is essential for developing effective, eco-friendly soil remediation agents. This study investigates the mechanisms by which cystamine-modified biochar (Cys-BC) alleviates cadmium (Cd) toxicity in lettuce, comparing its effects to those of raw biochar across key parameters: plant growth, antioxidant enzyme activities, available Cd in root-sheet-soil, and shifts in microbial communities. Results Cys-BC significantly enhances biomass, increasing above-ground growth by 40.54–44.95% and root biomass by 37.54–47.44% compared to Cd-stressed controls. Photosynthetic parameters, including chlorophyll a content and net photosynthetic rate, improve by up to 91.02% and 37.93%, respectively. Cys-BC mitigates oxidative stress, enhancing antioxidant activities by 73.83–99.39%. Additionally, it reduces available soil Cd levels while promoting microbial diversity, as evidenced by increases in Shannon, Chao1, and ACE indices of 12.81%, 14.48%, and 17.15%, respectively. Conclusions Cys-BC enhances glutathione reductase activity and increase cysteine levels within the ascorbate-glutathione cycle, functioning through increased soil cation exchange for Cd passivation rather than through pH modifications. Significant shifts in microbial communities, particularly the increases in Deltaproteobacteria and Nitrospira , underscore their roles in sulfur and nitrogen metabolism. These findings provide new insights into how modified biochar, specifically Cys-BC, can effectively address Cd contamination, highlighting its potential for broader applications in soil remediation.