Plant Physiology

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Chapter 10 Study Questions

  1. Leaves of aquatic plants living under water are devoid of stomata. Leaves that float in water have stomata in the upper surface growing in contact with air, but lack them in the surfaces that are in contact with water. Aerial leaves have stomata in both surfaces. Explain.

    Textbook Reference: Introduction, p. 269

  2. Explain the statement: “Guard cells are turgor valves.”

    Textbook Reference: Introduction, p. 270

  3. What is the relationship between the level of incident solar radiation at the leaf surface, and stomatal movements.

    Textbook Reference: Light-dependent Stomatal Opening, p. 270

  4. What are the the two major factors responsible for light-dependent stomatal opening?

    Textbook Reference: Light-dependent Stomatal Opening, pp. 270‐271

  5. What are “saturating levels of light”? Under red light levels that saturate the photosynthetic response, a small amount of blue light causes a large stomatal response. Explain.

    Textbook Reference: Light-dependent Stomatal Opening, p. 271

  6. When guard cell protoplasts are irradiated with blue light under saturating background red light illumination, the pH of the suspension medium becomes more acidic. Explain why the acidification is best explained as the activation of a proton pump by blue light.

    Textbook Reference: Light-dependent Stomatal Opening, p. 272

  7. Compare and contrast stomatal opening driven by: 1. starch-sugar interconversion, and 2. the uptake of potassium and its counterions.

    Textbook Reference: Light-dependent Stomatal Opening, pp. 273‐ 275

  8. Explain the relationship between the daily courses of changes in stomatal apertures and the changes in potassium and sucrose content in guard cells.

    Textbook Reference: Light-dependent Stomatal Opening, p. 275

  9. Describe the phenotypes of the npq1 and phot1/phot2 mutants.

    Textbook Reference: Mediation of Blue-light Photoreception in Guard Cells by Zeaxanthin, p. 276

  10. Describe the xanthophyll cycle in the mesophyll chloroplast and in the guard cell chloroplast.

    Textbook Reference: Mediation of Blue-light Photoreception in Guard Cells by Zeaxanthin, pp. 276‐277

  11. A green-light pulse blocks the opening stomatal response to a blue-light pulse, and a second blue-light pulse given after the green-light pulse restores the opening response. Explain.

    Textbook Reference: Reversal of Blue Light-Stimulated Opening by Green Light, p. 279

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