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Now let's look at an example in a plant cell from a leaf. Use the slider to examine a plant cell before and after the plant was watered with very salty water. After watering with salt water, the plant wilted. Propose an explanation as to why the plant wilted using evidence from the cell diagrams.

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To understand why a plant wilts after being watered with very salty water, we can examine the effects of osmotic pressure on plant cells, especially in the context of the diagrams of the plant cells before and after exposure to salty water.

Before Watering with Salty Water:

  • In the healthy plant cell, you would typically observe a turgid cell, characterized by:
    • A central vacuole filled with water, pushing against the cell wall.
    • The cytoplasm pressing against the cell wall, creating turgor pressure which helps maintain the cell's shape and firmness.
    • Chloroplasts and other organelles distributed evenly within the cytoplasm.

After Watering with Salty Water:

  • After exposure to salty water, the plant cell would show signs of wilting characterized by:
    • A shrinkage of the central vacuole, leading to reduced turgor pressure.
    • The cell membrane may pull away from the cell wall in a process known as plasmolysis. This occurs because water is drawn out of the cell to balance the higher solute concentration (salts) outside the cell.
    • The cytoplasm may appear more concentrated as water leaves the cell.

Explanation for Wilting:

When the plant is watered with very salty water, osmosis occurs due to the difference in solute concentration inside and outside the plant cells. The water inside the plant cells moves out to the exterior to dilute the higher concentration of solutes (salt) outside the cell. This loss of water results in:

  1. Decreased Turgor Pressure: The reduction in the vacuole’s water content leads to lower turgor pressure, which is crucial for maintaining the structural integrity of the plant cells.
  2. Plasmolysis: The cell membrane retreats from the cell wall, causing the plant to lose its firmness and ultimately leading to wilting.
  3. Effects on Photosynthesis and Nutrient Transport: Reduced cell turgidity affects overall plant functions, including photosynthesis and nutrient transport, contributing to the health decline of the plant.

In conclusion, the wilting of the plant after watering with salty water can be attributed to the osmotic movement of water out of the cells, resulting in decreased turgor pressure and structural integrity, as evidenced by the changes observed in the cell diagrams before and after exposure to the saline environment.