This study investigates the effects of adding 5% (w/w) biochar to saline soils on lettuce (Lactuca sativa L.) plants, with NaCl concentrations ranging from 0 to 400 mM. The research aims to find eco-friendly solutions to mitigate the negative impacts of soil salinity, a significant environmental concern. Biochar, a product derived from plant biomass through pyrolysis, was tested for its ability to alleviate salt stress on lettuce plants. The study assessed the biometric, physiological, and biochemical parameters of lettuce plants over a four-week period. Key findings include: - NaCl concentrations above 100 mM negatively affected lettuce plants, leading to reduced chlorophyll content, fresh weight, and increased electrolyte leakage. - Biochar, at 5% (w/w), showed some effectiveness in mitigating the negative effects of salt stress, particularly at concentrations up to 200 mM NaCl. It increased chlorophyll content, fresh weight, and total antioxidant power. - Biochar did not significantly reduce Na accumulation in lettuce leaves but enhanced the expression of several parameters, such as total antioxidant power, fresh weight, chlorophyll content, total soluble protein, and K content. - The addition of biochar did not influence the content of free amino acids in lettuce leaves but increased their expression in some cases. - Overall, the study suggests that biochar is a viable solution to counteract the damage caused by high salt concentrations on plant growth, particularly at concentrations up to 200 mM NaCl. The research highlights the potential of biochar as an eco-friendly approach to address soil salinity issues, which are becoming increasingly prevalent due to climate change and agricultural practices.This study investigates the effects of adding 5% (w/w) biochar to saline soils on lettuce (Lactuca sativa L.) plants, with NaCl concentrations ranging from 0 to 400 mM. The research aims to find eco-friendly solutions to mitigate the negative impacts of soil salinity, a significant environmental concern. Biochar, a product derived from plant biomass through pyrolysis, was tested for its ability to alleviate salt stress on lettuce plants. The study assessed the biometric, physiological, and biochemical parameters of lettuce plants over a four-week period. Key findings include: - NaCl concentrations above 100 mM negatively affected lettuce plants, leading to reduced chlorophyll content, fresh weight, and increased electrolyte leakage. - Biochar, at 5% (w/w), showed some effectiveness in mitigating the negative effects of salt stress, particularly at concentrations up to 200 mM NaCl. It increased chlorophyll content, fresh weight, and total antioxidant power. - Biochar did not significantly reduce Na accumulation in lettuce leaves but enhanced the expression of several parameters, such as total antioxidant power, fresh weight, chlorophyll content, total soluble protein, and K content. - The addition of biochar did not influence the content of free amino acids in lettuce leaves but increased their expression in some cases. - Overall, the study suggests that biochar is a viable solution to counteract the damage caused by high salt concentrations on plant growth, particularly at concentrations up to 200 mM NaCl. The research highlights the potential of biochar as an eco-friendly approach to address soil salinity issues, which are becoming increasingly prevalent due to climate change and agricultural practices.