Gas Exchange in Plants: Practical 7.9
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Questions and Answers

What indicates a higher than normal level of carbon dioxide in a hydrogencarbonate indicator?

  • Green
  • Purple
  • Red
  • Yellow (correct)
  • What does tube A's outcome suggest about the gas exchange in leaves during light conditions?

  • Leaves absorb carbon dioxide. (correct)
  • Leaves release carbon dioxide.
  • Leaves only produce oxygen.
  • Leaves do not exchange gases.
  • Which of the following best explains the role of tubes B and D in the experiment?

  • They directly measure oxygen production.
  • They demonstrate the process of photosynthesis.
  • They serve as control tubes to validate results. (correct)
  • They contain a higher CO2 concentration initially.
  • What was the color of the hydrogencarbonate indicator in tube C after five hours under light conditions?

    <p>Yellow</p> Signup and view all the answers

    Under dark conditions, what is observed in tube C compared to tube D?

    <p>Tube C shows a color change while tube D does not.</p> Signup and view all the answers

    Which condition is responsible for the change observed in tube A after five hours?

    <p>Presence of green leaves.</p> Signup and view all the answers

    What process takes place in green plants during photosynthesis?

    <p>Using carbon dioxide and producing oxygen.</p> Signup and view all the answers

    What color indicates a normal level of carbon dioxide in a hydrogencarbonate indicator?

    <p>Red</p> Signup and view all the answers

    What is the primary reason for the net uptake of carbon dioxide in plants during light conditions?

    <p>Photosynthesis consumes more carbon dioxide than respiration produces.</p> Signup and view all the answers

    What occurs in plants during dark conditions regarding gas exchange?

    <p>Respiration continues, resulting in a net release of carbon dioxide.</p> Signup and view all the answers

    Which structure in plants is primarily responsible for gas exchange?

    <p>Stomata</p> Signup and view all the answers

    During which condition do plants produce more oxygen than they use?

    <p>During daylight when photosynthesis is active.</p> Signup and view all the answers

    What will likely happen if a plant's stomata are blocked?

    <p>Reduced gas exchange.</p> Signup and view all the answers

    Which of the following best describes the relationship between photosynthesis and respiration in light conditions?

    <p>Photosynthesis outpaces respiration, leading to net gas exchange results.</p> Signup and view all the answers

    Study Notes

    Gas Exchange in Plants

    • Green plants use photosynthesis to create food, consuming carbon dioxide and releasing oxygen.
    • Respiration releases energy from consumed food, requiring oxygen and releasing carbon dioxide.
    • The absorption and release of gases by plants changes throughout the day.
    • Practical 7.9 explores carbon dioxide uptake or release in plants.

    Practical 7.9: Studying Uptake or Release of Carbon Dioxide in Plants

    • Aim: To observe how carbon dioxide levels change in tubes with leaves, under different light conditions.
    • Apparatus and materials: boiling tubes, cotton thread, fresh green leaves, aluminium foil, test tubes rack, measuring cylinder (10 cm³), hydrogencarbonate indicator, table lamp.
    • Procedure:
      • Add indicator to four tubes (A, B, C, D).
      • Note the initial indicator colour.
      • Put leaves in tubes A and C, then seal.
      • Seal tubes B and D. Cover tube C with foil.
      • Expose the set-ups to light for 5 hours.
      • Note the change in indicator colour in each tube.

    Hydrogencarbonate Indicator

    • Different colours correspond to different carbon dioxide levels.
    • Purple = lower carbon dioxide levels.
    • Red = normal levels in air (approximately 0.04%).
    • Yellow = Higher carbon dioxide levels.

    Results and Discussion

    • Tube A (light, leaves): Indicator colour changes to purple, indicating carbon dioxide uptake.
    • Tube B (light, no leaves): Indicator stays red, serving as a control.
    • Tube C (dark, leaves): Indicator colour changes to yellow, suggesting carbon dioxide release.
    • Tube D (dark, no leaves): Indicator remains red, serving as a control.
    • These results show that plants take in carbon dioxide in light and release it in the dark.

    Net Gas Exchange in Plants (Light and Dark)

    • Light conditions: Plants take in more carbon dioxide in photosynthesis than they produce in respiration, resulting in a net uptake of carbon dioxide. Photosynthesis produces more oxygen than respiration uses, resulting in a net oxygen release.
    • Dark conditions: Plants only carry out respiration (no photosynthesis). This leads to a net release of carbon dioxide and net oxygen uptake.

    Gas Exchange Through Stomata

    • Stomata are pores on leaf surfaces enabling gas exchange.
    • They allow carbon dioxide and oxygen to enter and exit the leaf.

    Observing Stomata

    • Practical 7.11 demonstrates observing stomata under a microscope.
    • Specific leaf epidermis, preparation, magnification (low and high) are important details.
    • Drawings are essential; diagrams should include labelled drawings of stomata and surrounding cells.

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    Description

    Explore the mechanisms of gas exchange in plants through practical experiments. This quiz focuses on carbon dioxide uptake and release under varying light conditions, utilizing different apparatus and procedures. Understand the role of photosynthesis and respiration in plant biology.

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