1. Gas Exchange in Plants What are the two main gases that all organisms on earth need to exchange back and forth between themselves and the environment? OXYGEN AND CARBON DIOXIDE

2. Why do autotrophs and heterotrophs need to exchange these gases? A. Autotrophs SUCH AS... 1. Need CO 2 for photosynthesis. 2. Use O 2 for cellular respiration. 3. Get rid of excess O 2 through... STAY TUNED!

3. Why do autotrophs and heterotrophs need to exchange these gases? B. Heterotrophs SUCH AS... 1. Use O 2 for cellular respiration. 2. Get rid of CO 2 as a waste gas.

4. How do flowering plants exchange these gases? They use three vegetative structures: 1.Roots 2.Stems 3.Leaves

5. How do flowering plants exchange these gases? 1. Roots a. CO 2 dissolves in water in soil. b. CO 2 absorbed by root hairs; transported by xylem c. Photosynthesis produces O 2 ; transported by phloem.

6. How do flowering plants exchange these gases? 2. Stems a. Lenticels – tiny openings in stems for gas exchange. (white “spots” are the openings)

7. How do flowering plants exchange these gases? 3. Leaves a. Review leaf’s cross-section structure. Cuticle Upper epidermis Lower epidermis Palisade layer Spongy layer Guard cells and stomata

8. How do flowering plants exchange these gases? 3. Leaves b. O 2 and CO 2 AND H 2 O are exchanged at stomata formed by guard cells. c. Guard cells are in OPEN position when filled with water and CLOSED when water is scarce. Guard cell Animation

9. How do flowering plants exchange these gases? 3. Leaves d. What type of plant would be most likely found in the rainforest? One with lots of guard cells or one with few guard cells? LOTS OF GUARD CELLS – WHY?

10. How do flowering plants exchange these gases? 3. Leaves e. Gas exchange also happens at spongy layer and palisade layer.