Copper and cadmium toxicity affecting in vitro growth and Scopelophila cataractae development

The effects of copper (Cu) and cadmium (Cd) accumulation on growth and development of Scopelophila cataractae (Mitt.) Broth., Pottiaceae, were investigated over 24 weeks. Moss samples were grown on modified hydroponic medium supplemented with Cu and Cd. Cu markedly promoted the transition from chloronema to caulonema and showed a significantly higher proportion (95.5%) at 800 µM CuSO₄. The greatest bud and gametophore formation was observed in the 400 µM CuSO₄ treatment, with 130 buds per 25 mm². In contrast, Cd restricted filaments to the chloronema stage, reduced average chloroplast numbers per cell (from 75 to 34.5 under 800 µM CdCl₂), and induced large vacuolar vesicles, reflecting cellular stress. Relative growth rates were 7.1, 10.7 and 16.2 mg g⁻¹d⁻¹ for 800 µM CuSO₄, 800 µM CdCl₂ and control, respectively, indicating strong growth inhibition by heavy metals at high accumulation. Co-exposure of low Cu with Cd increased Cd accumulation (2,188 to 16,027 mg kg⁻¹) and mitigated Cd toxicity. High metal accumulation (>1,000 mg kg⁻¹ for Cd, >10,000 mg kg⁻¹ for Cu), protonemal growth and development were generally suppressed. These findings highlight the adaptive strategies of S. cataractae in coping with heavy metal stress and its potential as a bioindicator for metal-contaminated environments. • Scopelophila cataractae exposed to low Cd levels retained protonema, without buds or gametophores • Low Cd accumulation in S. cataractae increased chloroplasts by 5–10 per cell • Only Cu induced chloronema-to-caulonema transition, bud, and gametophore formation in S. cataractae • Low Cd accumulation in S. cataractae protonemata is due to Cd detoxification in vacuoles • Scopelophila cataractae can be used as a bioindicator and phytoremediator of Cu and Cd