Comparative tolerance and phytoremediation potential of four Lagerstroemia indica cultivars under cadmium stress

Woody ornamentals hold significant promise for phytoremediation. However, the cadmium (Cd) tolerance and accumulation ability of the commonly planted Lagerstroemia indica, have not been insufficiently studied. This study evaluated four L. indica cultivars (‘Red Rocket’, ‘Pink Velour’, ‘Dynamite’, and ‘Black Diamond’) under soil Cd stress (0, 10, 50, and 100 mg·kg− 1) in an 80-day pot experiment. Significant intraspecific variation in Cd tolerance was observed, reflected in distinct growth and Cd accumulation strategies. ‘Dynamite’ showed a hormetic growth response at 10 mg·kg− 1 Cd but suffered complete mortality at 100 mg·kg− 1 Cd, indicating low tolerance and limited phytoextraction potential. In contrast, ‘Red Rocket’ and ‘Black Diamond’ demonstrated a consistent phytostabilization strategy. They maintained stable growth (tolerance index, TI > 1.0) at the highest Cd level (100 mg·kg− 1), characterized by effective root Cd retention with high root bioconcentration factors (BCFs > 1.0) and low translocation factors (TFs < 1.0). ‘Pink Velour’ displayed a plastic response. It showed a balanced root-shoot distribution (TF > 1.0) at 50 mg·kg− 1 Cd, but under high stress (100 mg·kg− 1), it showed pronounced root sequestration (TF < 1.0). This confirms phytostabilization as its primary tolerance mechanism. These cultivar-specific strategies highlight the potential of selecting specific L. indica cultivars for the phytomanagement of Cd-contaminated soils.