How is turgor pressure primarily maintained in plant cells?

Turgor pressure in plant cells is primarily maintained by the presence of water in vacuoles. The vacuole is a large, membrane-bound organelle that stores water and various solutes. When the vacuole is filled with water, it exerts pressure against the cell wall, creating turgor pressure, which helps maintain cell structure and rigidity. This pressure is essential for supporting the plant and enabling it to remain upright.

The role of vacuoles is crucial because they can store a significant amount of water, allowing plants to regulate their internal water balance effectively. When water enters the vacuole through osmosis, it increases the volume, which in turn increases turgor pressure. This pressure drives the expansion of the cell and contributes to overall plant growth.

While osmotic processes are important in facilitating the movement of water into the vacuole, it is the presence of water itself in the vacuole that directly contributes to turgor pressure. Hence, the correct answer emphasizes the key role of vacuoles filled with water in maintaining this vital pressure in plant cells.