How do microtubules help direct the deposition of cellulose in the plant cell wall?
A.
The orientation of the newly deposited extracellular cellulose microfibrils is determined by the orientation of the underlying intracellular microtubules.
B.
The large cellulose synthase enzyme complexes are integral membrane proteins that continuously synthesize cellulose microfibrils on the outer face of the plasma membrane.
C.
The distal ends of the stiff microfibrils become integrated into the texture of the cell wall, and their elongation at the other end pushes the synthase complex along in the plane of the plasma membrane. The microtubules serve as tracks that help guide the movement of the enzyme complexes.
D.
The cortical array of microtubules attached to the plasma membrane by transmembrane proteins helps determine the direction in which the microfibrils are laid down. In this curiously indirect way, the cytoskeleton controls the shape of the plant cell and the modeling of the plant tissues.