The correct answer is: Microtubules of the plant cell cortex are thought to affect the movement of cellulose-synthesizing enzymes in the cell membrane, which, in turn, affect cell wall growth and shape.
Plants have the ability to control the direction of cell expansion as a way of shaping growth. Microtubules are structures that help them to regulate the direction of growth. For example, transverse microtubules within the plant cell have the role to constrain the movement of cellulose synthase complexes that are essential for elongation growth.