Inelastic Cell Wall and Water

Plants cells have inelastic walls.

Water moves back and forth from cells to their surroundings by the process of osmosis. Cells with elastic walls expand as water enters into them; if too much water moves into such a cell, the cell will burst. Most plants contain cells that have inelastic cell walls. This allows water to enter the cell as needed without destroying the cell.

What Is Osmosis?

Osmosis is the process by which water moves through cells. If a cell or group of cells with a low concentration of water is placed in an area that has a higher concentration, the water tends to move to the more highly concentrated area. The water flows through the membrane of the cells, which is semi-permeable. This means that the cell membrane allows liquids to pass through it but does not allow minerals to pass through.

Osmosis and Elastic Membranes

Many cells, including the cells in the human body, have elastic membranes. When water flows into the cell, the elastic membrane allows the cell to expand. If too much water enters the cell, the cell can expand past its limit and burst. Conversely, if too much water flows out of the cell, the cell can shrivel up and die. Both of these conditions can occur in human beings. Dehydration occurs when there is not enough water in the body to keep cells alive; water intoxication occurs when a person drinks too much water rapidly, causing cells to burst.

Plant Cells

Unlike human cells, plant cells contain an inelastic membrane. The membrane is still semi-permeable, allowing water to flow freely through, but the cell does not expand when water enters it. This protects cells from bursting because of an overabundance of water.

Turgor Pressure

Cells with inelastic membranes do not expand when water flows into them. Instead, the influx of water presses against the cell membrane. The more water entering the cell, the greater the pressure. This pressure is called Turgor pressure. As the Turgor pressure on a cell increases, the cell becomes more rigid. This rigidity helps the plant maintain its shape.

Flaccidity

When there is more water in the plant cells than in the surrounding environment, water moves out of the cells. The cells then begin to lose their shape. This condition is called flaccidity. Flaccidity causes plants to wilt. If flaccid plants are not given water, the cells will shrivel and die.

References

• DocStoc.com: The Working Plant Summary Sheet
• Ohio State: Cell Expansion and Differentiation