Plants wilt due to a loss of turgor pressure within their cells, which is directly related to osmosis. When a plant doesn't receive enough water, osmosis causes water to move out of the plant cells, leading to wilting.
The Role of Osmosis in Plant Wilting
Osmosis is the movement of water from an area of high water concentration to an area of low water concentration through a semi-permeable membrane (like the cell membrane). In plants:
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Normal Conditions: When a plant is well-hydrated, water moves into the plant cells via osmosis, filling the central vacuole. This creates turgor pressure, which pushes the cell membrane against the cell wall, making the plant firm and upright.
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Water Scarcity: According to the reference, when the plant is not being watered, water moves out of the cells by osmosis, as the concentration of water will be higher in the cell than outside, and water always moves down its concentration gradient. This means the water concentration outside the cells (in the surrounding soil or air) is lower than inside the cells. Therefore, water leaves the cells.
Consequences of Water Loss
As water leaves the plant cells:
- Loss of Turgor Pressure: The central vacuole shrinks, reducing turgor pressure.
- Cell Flaccidity: The cell membrane no longer pushes firmly against the cell wall, and the cell becomes flaccid.
- Wilting: When enough cells lose turgor pressure, the plant loses its rigidity and begins to wilt. Stems droop, and leaves become limp.
Example
Imagine a celery stalk left out of water. Initially, the stalk is crisp and firm. However, over time, the cells lose water to the drier surrounding air through osmosis. The cells lose turgor pressure, and the celery stalk becomes limp and bendable – it wilts.
Solution
The solution to wilting caused by lack of water is simple: water the plant! This increases the water concentration outside the cells, allowing water to move back into the cells via osmosis, restoring turgor pressure, and reviving the plant.
