Why do plants wilt when they do not get water?

Plants begin to wilt when they do not receive enough water because their central vacuoles become empty. When water is available again, the vacuoles fill back up and the plants stand up straight. So, what process enables plant vacuoles to refill with water?

Answer:

Osmosis

The process that allows the vacuoles of plants to fill back up with water after a period of wilting is osmosis. Osmosis is the movement of water molecules from a region of higher water potential to a region of lower water potential through a semi-permeable membrane. Water enters the vacuoles of plants osmotically once water becomes available in their cells. The availability of water in the cytosol makes it have a higher water potential than the cell sap. In this case, the vacuole membrane or the tonoplast acts as the semi-permeable membrane and allows water to diffuse into the vacuole.

Final Answer:

The process that enables vacuoles in plant cells to refill with water is called osmosis, facilitated by a mechanism known as osmoregulation. Lack of water makes the plant cell's cytoplasm hypertonic, causing water to leave the cells and the plant to wilt. Watering the plant reverses this effect, restoring the turgor pressure.

Explanation: Osmosis is a type of passive transport that involves the movement of water from an area of higher concentration to an area of lower concentration across a semi-permeable membrane. In plants, this is navigated by a mechanism known as osmoregulation.

When a plant is not watered, the cytoplasm inside its cells becomes hypertonic compared to its external environment and water begins to leave the cell. As a result, the plant starts to wilt due to a loss of turgor pressure, which is the pressure exerted by water inside the cell against the cell wall. Upon watering, water re-enters the cells, filling the vacuoles and restoring the turgor pressure, which consequently results in the plant standing back up.