Not All Plant Cells Have Chloroplasts

A common error is assuming every plant cell has chloroplasts. Only cells in the green parts of the plant (mainly leaves and green stems) contain chloroplasts because only these parts photosynthesise. Root cells, for example, do not have chloroplasts: they are underground and receive no light. This is a detail examiners specifically test.

The Role of Turgor Pressure

The large permanent vacuole in plant cells is filled with cell sap: a solution of sugars, mineral ions, and other substances in water. When the vacuole is full, it pushes the cytoplasm against the cell wall, creating turgor pressure. This pressure helps keep the plant upright and gives non-woody stems their rigidity. When plant cells lose water (e.g. In drought), the vacuole shrinks, turgor is lost, and the plant wilts. This process is called plasmolysis in extreme cases.