Soil lithium affects carrot growth by changing cation concentrations and physiological attributes

Lithium (Li) plays a significant role in human physiology and psychology; however, it is non-essential for plants. The extensive use of Li in industrial processes and battery-powered devices poses a potential global threat to living organisms. This study assessed the impact of varying soil Li concentrations (0, 20, 40, 60, and 80 mg/kg) on carrot (Daucus carota L.) plants. Results revealed that Li concentrations exceeding 40 mg/kg soil had detrimental effects on carrot growth. Compared to 0 mg/kg soil, Li concentrations of 60 and 80 mg/kg reduced shoot fresh biomass by 51% and 82%, respectively, and root fresh biomass by 68% and 89%, respectively. Elevated Li levels in the soil also increased hydrogen peroxide (H2O2) content in shoots and triggered enhanced activity of antioxidant enzymes, including superoxide dismutase (SOD) and catalase (CAT). Additionally, soil Li disrupted the uptake and translocation of essential nutrients such as potassium (K) and calcium (Ca) from roots to shoots. This study concludes that while low Li levels may elicit a positive response in plants, higher concentrations significantly impair growth and could contribute to the accumulation of Li in the food chain.