In an experiment, an Elodea plant is covered with foil and the volume of gas collected decreases. Why does this occur?

• A. The plant uses more carbon dioxide in the dark, increasing gas volume.
• B. The foil increases the temperature, causing more oxygen to be released.
• C. Covering the plant with foil increases water absorption, raising gas production.
• D. The absence of light prevents photosynthesis, so less oxygen is produced.

Answer: (D)

Verified step by step guidance

1. Step 1: Begin by understanding the role of photosynthesis in plants. Photosynthesis is the process by which plants use light energy to convert carbon dioxide and water into glucose and oxygen. This process occurs in the chloroplasts and requires light as a key component.
2. Step 2: Recognize that Elodea is an aquatic plant that performs photosynthesis. When light is available, the plant produces oxygen as a byproduct of photosynthesis, which can be collected as gas in an experiment.
3. Step 3: Analyze the effect of covering the plant with foil. The foil blocks light from reaching the plant, effectively simulating darkness. Without light, the plant cannot perform photosynthesis, and oxygen production decreases.
4. Step 4: Understand that the decrease in gas volume is due to the absence of oxygen production. In the dark, the plant may still perform cellular respiration, which consumes oxygen and releases carbon dioxide, but this does not increase the gas volume significantly.
5. Step 5: Conclude that the correct explanation is: 'The absence of light prevents photosynthesis, so less oxygen is produced.' This aligns with the observed decrease in gas volume in the experiment.