2.3 Gaseous Exchange and Respiration

• Gaseous exchange surfaces in plants
• Structure and function of stomata
• Mechanism of stomatal opening and closing
• Lenticels and gaseous exchange in stems and roots
• Aerobic and anaerobic respiration in plants

• describe gaseous exchange structures in plants
• explain the mechanism of opening and closing of stomata
• distinguish respiration from photosynthesis in plants
• describe aerobic and anaerobic respiration in plants
• appreciate the significance of gaseous exchange in plants

“Do plants breathe, and if so how?”

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1. Gaseous exchange in plants
   40 min · 2 practice tasks · quiz
   Stomata, lenticels, and the mechanism that opens and closes a pore with no muscles.
2. Respiration in plants
   40 min · 2 practice tasks · quiz
   Releasing energy from food, and why it is not the reverse of photosynthesis.
3. Why plants exchange gases
   40 min · 1 practice tasks · quiz
   Plants need carbon dioxide and oxygen for two different jobs, and both gases move by diffusion.
4. The leaf as a gas-exchange organ
   40 min · 1 practice tasks · quiz
   How cuticle, mesophyll and air spaces let gases reach every photosynthetic cell.
5. Structure and function of stomata
   40 min · 1 practice tasks · quiz
   Guard cells, the pore, and why only those epidermal cells have chloroplasts.
6. Factors that open and close stomata
   40 min · 1 practice tasks · quiz
   Light, carbon dioxide, water shortage and temperature set whether a pore is worth opening.
7. Where stomata are found
   40 min · 1 practice tasks · quiz
   Lower surfaces, both surfaces, upper surfaces of floating leaves, and sunken stomata.
8. Counting stomata on an epidermal peel
   40 min · 1 practice tasks · quiz
   Make a peel or varnish impression, count stomata, and compare upper and lower surfaces.
9. Lenticels on woody stems and roots
   40 min · 1 practice tasks · quiz
   When bark replaces the epidermis, loosely packed lenticels keep a diffusion path open.
10. Gaseous exchange in roots
    40 min · 1 practice tasks · quiz
    Roots take oxygen from soil air spaces; flooding fills those spaces and the root is starved.
11. Aerobic respiration in plant cells
    40 min · 1 practice tasks · quiz
    The word and symbol equations, complete breakdown of glucose, and where the steps happen.
12. Mitochondria in plant cells
    40 min · 1 practice tasks · quiz
    Cristae, matrix, and why meristems and root hairs are packed with mitochondria.
13. ATP as the energy currency of plant cells
    40 min · 1 practice tasks · quiz
    Respiration charges ATP; cell work spends it; glucose is the store, ATP is the coin.
14. How plants use energy from respiration
    40 min · 1 practice tasks · quiz
    ATP pays for ion pumps, growth, translocation, protein synthesis and opening stomata.
15. The compensation point
    40 min · 1 practice tasks · quiz
    Net gas exchange is the difference between photosynthesis and respiration, not a switch.
16. Anaerobic respiration and fermentation
    40 min · 1 practice tasks · quiz
    Without oxygen, plant and yeast cells make ethanol, carbon dioxide and little ATP.
17. Investigating CO2 from germinating seeds
    40 min · 1 practice tasks · quiz
    Lime water turns milky with carbon dioxide from living seeds; boiled seeds are the control.
18. Heat and oxygen use by germinating seeds
    40 min · 1 practice tasks · quiz
    A thermos of live seeds warms; a control of killed seeds does not. Respiration releases heat and uses oxygen.
19. Factors affecting the rate of respiration
    40 min · 1 practice tasks · quiz
    Temperature, oxygen, water and substrate decide how fast plant cells respire.
20. Brewing, baking and silage in Kenya
    40 min · 1 practice tasks · quiz
    People use plant and yeast fermentation for busaa, bread, biogas ideas and livestock silage.
21. Waterlogging, rice and aerenchyma
    40 min · 1 practice tasks · quiz
    Flooded maize dies of oxygen shortage; rice and mangroves pipe air to their roots.
22. Why gaseous exchange in plants matters
    40 min · 1 practice tasks · quiz
    A synthesis: structures, respiration, food security, and careers that use this biology.