Write the term for the pressure exerted by the cell contents on the cell wall.

TURGOR PRESSURE.

When a plant cell takes in water by endosmosis, the vacuole swells and the protoplasm presses outward against the cell wall. That outward push is TURGOR PRESSURE, and the cell is then said to be TURGID.

THE PARTNER TERM, which is often asked alongside: WALL PRESSURE is the equal and opposite inward push exerted by the rigid cell wall on the contents. The two balance, which is what stops the cell from bursting — and why a plant cell can be placed in pure water safely while an animal cell would swell and burst.

WHY IT MATTERS TO THE PLANT: turgor pressure is what keeps herbaceous stems and leaves firm and upright. When it is lost, the cells become FLACCID and the plant WILTS — the same phenomenon described in Question 3(iv) of this paper.