Melatonin Mitigates Cadmium-Induced Oxidative Damage and Modulates Polysaccharide Biosynthesis in Bletilla striata

Cadmium (Cd), a highly toxic heavy metal, poses severe risks to ecosystem stability and human health. The medicinal plant Bletilla striata, valued for its polysaccharide-rich rhizomes, demonstrates notable tolerance to Cd stress. Melatonin (MT), an indoleamine phytohormone, has emerged as a key regulator enhancing plant resilience to heavy metal toxicity. Nevertheless, the molecular mechanisms governing MT-mediated biosynthesis of Bletilla striata polysaccharides (BSP) under Cd exposure, along with its role in counteracting Cd-induced oxidative damage, remain inadequately characterized. Here, we applied integrated transcriptomic and metabolomic analyses to elucidate MT's regulatory influence on BSP biosynthesis under Cd stress.