Final answer:
The primary function of a vacuole in plant cells is temporary storage of items like water and nutrients, and to maintain turgor pressure against the cell wall, which is essential for plant structure and growth.
Step-by-step explanation:
The Primary Function of a Vacuole in Plant Cells
The primary function of a vacuole in plant cells is temporary storage of water, waste products, food, and cellular material. Plant cells have a large central vacuole that can occupy up to 90% of the cell's volume. The vacuole is surrounded by a membrane called the tonoplast. The vacuole's main role is to maintain turgor pressure against the cell wall, which is vital for keeping the plant upright and aiding in growth. Proteins in the tonoplast regulate water flow, helping the plant respond to environmental changes like drought, which can cause wilting when the vacuole loses water. The central vacuole also stores pigments that color flowers and compounds that discourage herbivory.
In summary, the central vacuole is essential for water regulation, turgor pressure maintenance, storage of important substances, and cell enlargement without the high energy cost of synthesizing new cytoplasm.