Leaves and Photosynthesis

Goals and Objectives:

  1. Be able to describe the three major themes that have been involved in the evolution of plant leaves.
  2. Be able to explain how a plant leaf handles the dual problems of obtaining carbon dioxide for photosynthesis while maintaining a sufficient water balance.
  3. Be able to diagram and label the structures in a cross section of a dicot and monocot leaf.
  4. Be able to explain the structure/function relationship in a plant leaf.
  5. Be able to explain how stomata are able to increase carbon dioxide intake, and water loss.
  6. Be able to describe the mechanisms involved in stomatal opening and closing.
  7. Be able to analyze the interplay between several environmental conditions that would affect stomatal opening and closing.


Study Questions:
  1. What are the three evolutionary modifications that we see in plants that have allowed plants to become efficient at absorbing light energy while conserving water? (pages 143-144)
  2. With these three evolutionary modifications in mind, how do  plant structures and physiology  in algae and bryophyts deal with these three aspects of photosynthesis? (pages 144-146)
  3. With these three evolutionary modifications in mind, how do  higher plant structures and physiology  deal with these three aspects of photosynthesis? (page 147)
  4. How are the internal structures of a plant leaf constructed so as to absorb the maximum amount of light? (pages 147-148)
  5. How are the structures of a plant leaf designed to facilitate absorption of carbon dioxide? (pages 148-150)
  6. Why do small pores (like stomata) increase diffusion?  Relate this idea to the diffusion of water vapor and carbon dioxide into and out of the leaf by way of the stomata.  (page 152)
  7. Describe how the structure of the guard cells allows the opening of  the stomatal apparatus. (page 152)
  8. Describe how the physiology within the guard cells allows the opening of the stomatal apparatus.  (page 153-154)
  9. The study of stomatal opening and closing has been difficult.  Mainly because so many environmental factors impinge on the functioning of the guard cells.  Describe how each of the following would affect the opening and closing of the stomatal apparatus: (pages 154-157)