Root hairs are tubular outgrowths of root epidermal cells in plants. These outgrowths help plants absorb water and nutrients by increasing root surface area. Root hairs form when membrane-bound structures inside root epidermal cells carry macromolecules to one side of the cell. There, the structures fuse with the plasma membrane, releasing their contents outside the cell. The released macromolecules are then incorporated into the elongating cell wall of the root epidermal cell, which allows the root hair to continue growing.
A group of scientists discovered a plant that had no root hairs. The scientists determined that this phenotype was due to a genetic mutation that inhibited the process by which root hair growth takes place. This mutation was located in the rth1 gene.
Based on the information above, which of the following cell processes did the rth1 mutation most likely inhibit in the plant with no root hairs?
A. Facilitated diffusion through membrane channels
B. Vesicle fusion during exocytosis
C. Receptor-mediated endocytosis
D. Membrane transport mediated by transmembrane ATPases