Forming the cell walls of stems, leaves, and roots, what compound is the primary structural constituent of plant tissues?

cellulose

Explanation:

Cellulose is plant constituent composed of a huge number of glucose units. It is the main structural component of the primary cell wall of plants. Cellulose is usually in mixture with hemicellulose, lignin and pectin. Because of its structure, cellulose is responsible for the strenght and rigidity od plant cells.