Final answer:
The water is rushing into the tonoplast, a membrane-bound organelle with a high ion concentration in plant cells. This influx of water creates turgor pressure which stiffens the cell walls of the plant, making the flowers stand upright again.
Step-by-step explanation:
The water is rushing into the tonoplast, which is a membrane-bound organelle with a high ion concentration in plant cells.
In plants, the cytoplasm is always slightly hypertonic compared to the cellular environment. When the flowers are refilled with water, it enters the cell and moves into the cytosol and then into the tonoplasts, resulting in higher osmotic pressure inside the tonoplasts. This influx of water creates turgor pressure which stiffens the cell walls of the plant, making the flowers stand upright again.