Role of 6-benzylaminopurine in modulating pigment biosynthesis and physiological resilience in Cd-stressed <i>Strobilanthes alternata</i>

Contamination of soil by cadmium is an emerging urgent issue of human concern. The present study was conducted to investigate the effects of 250 mg/kg cadmium chloride (CdCl₂) and 25 ppm of 6-benzylaminopurine (6-BAP) on pigment constitution, <i>ChlM</i> gene expression, antioxidant activity, and secondary metabolite profile in <i>Strobilanthes alternata</i>, a herbaceous plant with excellent Cd phytostabilization potential. The results revealed that 6-BAP could enhance the total chlorophyll (52%) and carotenoid contents (57%), <i>ChlM</i> gene expression (1.4-fold in leaves), glutathione contents (ninefold in roots, onefold in leaves), superoxide dismutase (SOD, 27% in roots, 19% in leaves), catalase (1.5-fold in roots), ascorbate peroxidase (APX, eightfold in roots), and guaiacol peroxidase (GPOX, 3.9-fold in roots) activities in Cd-stressed plants compared to Cd treated <i>S. alternata</i>. The liquid chromatography-mass spectrometry (LC-MS) analysis revealed the presence of putative protective compounds like verproside, atractyloside, 4-(4-hydroxyphenyl)-2-butanone O-[2-galloyl-6-p-coumaroylglucoside], pallidol 3,3″-diglucoside, ent-fisetinidol-(4beta->8)-catechin-(6->4beta)-ent-fisetinidol, (-)-matairesinol 4'-[apiosyl-(1->2)-glucoside], and notoginsenoside Fe only in Cd + 6-BAP treated <i>S. alternata.</i> These results reveal the capability of 6-BAP as an efficient amendment for enhancing heavy metal stress resilience in plants. Further studies are required to validate the efficiency of this method in different plants under field conditions.