Answer:
Lignin.
Explanation:
Lignin is a material whose deposition is responsible for the thickening of cell walls of sclerenchyma tissue. Lignin is a organic material present in the cell of the cell. It is responsible for transport of water, provide support to the plant and provide resistance to various stresses. It is mostly present in the woody stem of the tree make the stem rigid and protected the stem against pathogens.
