Examkin

Question

Difficulty: MediumPlant Biology and Photosynthesis

During periods of severe drought, terrestrial plants must conserve moisture while still acquiring gases needed for photosynthetic reactions. Which specialized epidermal cells regulate transpiration and gas exchange by altering their shape to open and close leaf pores?

  1. A
    Centrioles
  2. B
    Mitochondria
  3. Guard cellsAnswer
  4. D
    Epithelial cells

Answer

The specialized epidermal cells that regulate transpiration and gas exchange by opening and closing leaf pores are guard cells.
Guard cells are specialized kidney-shaped cells located in the leaf epidermis that flank each stomatal opening. When the plant is well-hydrated, guard cells fill with water, become turgid, and bow outward to open the pore for gas intake. Under drought conditions, the cells lose water and deflate, sealing the pore to prevent desiccation.

Step-by-Step Solution

1
Identify the primary mechanism of gas exchange and transpiration in plant leaves.
Leaves contain microscopic pores called stomata that permit the intake of carbon dioxide and the release of oxygen and water vapor.
Understanding how gases enter and exit the leaf establishes the anatomical focus of the question.
2
Determine which specialized cells control the opening and closing of these pores.
Paired guard cells flank each stoma and regulate its aperture through changes in internal water pressure.
When guard cells gain water, they swell and curve outward to open the pore; when water is scarce, they lose turgidity and close the pore to conserve moisture.

Key Concept

Stomatal regulation of gas exchange and transpiration by guard cells
Estimated Time:1m 0s
Rate this question

Topics

Plant Biology and Photosynthesis

More questions from this topic