Germination of Paulownia elongata S.Y. Hu seeds under heavy metal-induced stress conditions

The germination of Paulownia elongata seeds under heavy metal-induced stress is critical for its potential use in phytoremediation of contaminated soils. Understanding how heavy metals affect early growth stages of P. elongata helps evaluate its tolerance and suitability for soil remediation. This study examines the effects of varying concentrations of MnCl₂, CdCl₂, ZnCl₂, FeCl₂, and NaCl on seed germination percentage, germination energy, relative germination index (RGI), mean germination time (MGT), and root growth. Germination tests were conducted under controlled conditions with concentrations ranging from 10³ mol/m³ to 10⁻³ mol/m³, alongside a control group treated with distilled water. Results indicated a concentration-dependent inhibitory effect for all tested salts. At 10³ mol/m³, germination was completely inhibited, demonstrating acute toxicity. Cd²⁺ showed the highest toxicity, with germination rates dropping to 66.8% at 10⁻³ mol/m³, prolonged MGT, and low RGI values, highlighting its detrimental impact on plant development. Mn²⁺ and Na⁺ exhibited less severe effects compared to other metals. These findings underscore the sensitivity of P. elongata to heavy metal stress, particularly at higher concentrations. Further research is needed to explore the species’ adaptive mechanisms, including metal uptake dynamics, antioxidant production, and the regulation of genes linked to abiotic stress tolerance. Such studies could enhance the application of P. elongata in sustainable remediation strategies for polluted environments.