Correct Option: B. A very strong sugar solution
Explanation of the Correct Answer:
- Understanding Plasmolysis:
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Plasmolysis is a process that occurs in plant cells when they lose water due to osmosis. This typically happens when a cell is placed in a hypertonic solution (a solution with a higher solute concentration than the cell's cytoplasm). In this case, water moves out of the cell to balance the solute concentrations, causing the cell membrane to pull away from the cell wall.
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Analyzing Solution X:
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Since the spirogyra cell was plasmolysed after being placed in solution X, we can conclude that solution X must be hypertonic relative to the internal environment of the spirogyra cell. This means that solution X has a higher concentration of solutes (like sugar) compared to the cytoplasm of the spirogyra.
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Why Option B is Correct:
- A very strong sugar solution is hypertonic. When the spirogyra cell is placed in this solution, water will exit the cell to dilute the sugar outside, leading to plasmolysis. The strong concentration of sugar creates a significant osmotic gradient, driving water out of the cell quickly.
Why the Other Options are Incorrect:
- Option A: Tap Water:
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Tap water is typically a hypotonic solution compared to the cytoplasm of plant cells. If a spirogyra cell were placed in tap water, it would absorb water, swell, and potentially burst (lyse) rather than plasmolyse. Therefore, this option cannot cause plasmolysis.
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Option C: A Weak Sugar Solution:
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A weak sugar solution is likely to be closer to isotonic or only slightly hypertonic. In this case, the osmotic pressure would not be strong enough to cause significant water loss from the spirogyra cell. Thus, plasmolysis would not occur in a weak sugar solution.
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Option D: A Very Weak Salt Solution:
- A very weak salt solution is also likely to be hypotonic or only slightly hypertonic. Similar to the weak sugar solution, it would not create a strong enough osmotic gradient to cause water to leave the cell in significant amounts, preventing plasmolysis.
Summary of Key Points:
- Plasmolysis occurs when plant cells lose water in a hypertonic solution.
- Solution X must be hypertonic for plasmolysis to occur, which is why a very strong sugar solution (Option B) is correct.
- Hypotonic solutions (like tap water) cause cells to swell, while weak solutions (sugar or salt) do not create enough osmotic pressure to induce plasmolysis.
- Understanding osmotic gradients is crucial for predicting cell behavior in different solutions.