Stimulatory Effect of Aluminum in Root Development of Pogostemon cablin: Integration of ROS Homeostasis and Gene Expression Networks

On acid soils, aluminum (Al³⁺) is typically toxic to plants, though certain species like <i>Pogostemon cablin</i> (patchouli) show growth stimulation. This study reveals that Al functions as a root development stimulant in patchouli under acidic conditions. Treatment with 1.0 mM AlCl₃ for 34 days significantly enhanced root architecture, increasing total root length by 172.12% and root dry weight by 161.75%, without affecting shoot biomass. Structural analysis showed Al accumulation in root tip meristems and lateral root primordia, triggering a 103.77% increase in meristem activity and a 111.9% promotion of cell elongation. Physiological assays showed that Al treatment reduced H₂O₂ and malondialdehyde (MDA) levels by 49.2% and 67.6%, respectively, while boosting glutathione (GSH) content by 187.5%, thereby mitigating oxidative membrane damage mainly through the non-enzymatic antioxidant system. Moreover, Al deprivation impaired lateral root elongation, highlighting its functional importance. Gene expression profiling further indicated that Al regulated pathways related to cell proliferation, cell wall remodeling, and lateral root development. Taken together, our findings uncover a novel mechanism by which Al, traditionally regarded as toxic, acts as a stimulator of root development in patchouli, providing new insights into the molecular networks underlying plant abiotic stress responses.