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Questions and Answers
What conclusion can be drawn from the experiment where one part of a leaf is enclosed and the other is exposed to air?
What conclusion can be drawn from the experiment where one part of a leaf is enclosed and the other is exposed to air?
- Light is the only requirement for photosynthesis.
- CO₂ is necessary for photosynthesis. (correct)
- Photosynthesis occurs equally in both parts of the leaf.
- Only the enclosed part of the leaf can photosynthesize.
What did Joseph Priestley's experiments with a candle and a mint plant demonstrate?
What did Joseph Priestley's experiments with a candle and a mint plant demonstrate?
- Plants can survive without air.
- Plants can restore the air used by candles and animals. (correct)
- Candle combustion has no effect on air quality.
- Plants produce carbon dioxide.
What significant role did Jan Ingenhousz play in the study of photosynthesis?
What significant role did Jan Ingenhousz play in the study of photosynthesis?
- He demonstrated that plants do not need sunlight to survive.
- He showed that green parts of plants release oxygen in sunlight. (correct)
- He identified the process of photosynthesis in non-green plants.
- He discovered the molecular structure of chlorophyll.
Which of the following can be concluded from Priestley’s observations regarding a mouse, a candle, and a mint plant?
Which of the following can be concluded from Priestley’s observations regarding a mouse, a candle, and a mint plant?
What experimental setup did Ingenhousz utilize to demonstrate the need for sunlight in photosynthesis?
What experimental setup did Ingenhousz utilize to demonstrate the need for sunlight in photosynthesis?
How did the setup using KOH soaked cotton contribute to understanding photosynthesis?
How did the setup using KOH soaked cotton contribute to understanding photosynthesis?
What did the observation of bubbles forming around the green parts of the aquatic plant indicate?
What did the observation of bubbles forming around the green parts of the aquatic plant indicate?
What did Joseph Priestley conclude about the nature of air after conducting his experiments?
What did Joseph Priestley conclude about the nature of air after conducting his experiments?
What was the primary aim of Ingenhousz's experiments with plants?
What was the primary aim of Ingenhousz's experiments with plants?
What was the effect of enclosing a leaf part in a test tube with KOH soaked cotton?
What was the effect of enclosing a leaf part in a test tube with KOH soaked cotton?
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Study Notes
Photosynthesis Experiment
- A leaf segment can be isolated in a test tube with KOH-soaked cotton to absorb CO₂, while the other segment remains exposed to air.
- After exposure to light, testing for starch reveals that the exposed leaf part is positive, while the enclosed part is negative.
- This indicates that CO₂ is necessary for photosynthesis, as starch (a product of this process) is present only where CO₂ is available.
Early Experiments
- Joseph Priestley (1733–1804) conducted experiments in 1770 that demonstrated the importance of air for plant growth.
- He discovered oxygen in 1774 and observed that a candle extinguished in a closed space, similar to a mouse suffocating, indicating air is depleted.
- By placing a mint plant in the same enclosed space, he found that the mouse survived, and the candle continued to burn, leading him to hypothesize that plants restore air quality.
Methodological Insights
- To test whether the candle would burn after a period of being enclosed with a plant, it would need to be rekindled without disturbing the setup.
- Possible methods to light the candle include using a long taper or a match on a stick to reach the flame without opening the container.
Contributions of Jan Ingenhousz
- Jan Ingenhousz (1730-1799) built on Priestley's work by demonstrating the need for sunlight in photosynthesis.
- He used a setup similar to Priestley's, placing a plant in dark conditions and then in sunlight.
- His observation of bubbles forming around green plant parts in sunlight identified oxygen release, confirming that only green parts of plants can produce oxygen during photosynthesis.
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