Lignification-associated cell-wall responses contribute to cadmium tolerance in moso bamboo (Phyllostachys edulis)

Cadmium (Cd) is a highly toxic heavy metal that disrupts plant growth, photosynthesis and cellular homeostasis. Although Cd uptake, transport, and detoxification have been extensively studied in plants, how lignification-associated cell-wall remodeling contributes to Cd tolerance remains poorly understood, particularly in highly lignified woody grasses. Here, we used moso bamboo (Phyllostachys edulis) as a model to investigate whether lignification-associated responses participate functionally in the Cd stress response. Dose-response analysis showed that Cd caused progressive reduction of seedling growth and photosynthetic performance. At an early stage of exposure, Cd also induced redox imbalance and transcriptomic reorganization, including strong enrichment of phenylpropanoid- and lignin-associated pathways. These changes were accompanied by increased 4-coumarate:CoA ligase activity, accelerated lignin accumulation, stronger tissue lignification and thicker cell walls. Pharmacological perturbation provided additional support for the functional relevance of these responses. Treatment with 3,4-(methylenedioxy)cinnamic acid, which was used to suppress lignification-associated phenylpropanoid metabolism, intensified Cd-induced injury. Conversely, exogenous p-coumaric acid partially alleviated stress symptoms and promoted lignification-associated cell-wall responses. These contrasting treatments were also associated with altered Cd allocation between roots and leaves, with increased lignification stimulating root Cd sequestration and reduced leaf accumulation. Together, these findings indicate that lignification-associated cell-wall changes are closely associated with Cd tolerance in moso bamboo and may contribute to the Cd response, at least in part, by raising root Cd retention and restricting Cd accumulation in aerial tissues. This work therefore extends current understanding of heavy-metal stress biology in highly lignified woody species and provides a physiological basis for considering bamboo responses in the context of ecological restoration.