When does the plant lose stiffness and droop?

Explanation

### Step-by-Step Solution:

1. **Understanding Plant Cell Behavior**: Plant cells maintain their stiffness and structure due to a process called turgidity, which is the result of water entering the cells.

2. **Hypotonic Solution**: When a plant cell is placed in a hypotonic solution (where the concentration of solutes outside the cell is lower than inside), water enters the cell through a process called endosmosis. This causes the cell to swell and become turgid, maintaining its stiffness.

3. **Hypertonic Solution**: Conversely, when a plant cell is placed in a hypertonic solution (where the concentration of solutes outside the cell is higher than inside), water leaves the cell through a process called exosmosis. This leads to the cell shrinking and losing its turgidity.

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