Lecture Notes on Plant Respiration

Overview of Respiration in Plants

• Plants, like all organisms, require energy for bodily activities.
• They undergo both aerobic and anaerobic respiration.
• Diffusion is the mechanism for respiratory gas exchange in plants.

Key Processes in Respiration

• Glycolysis: Breakdown of glucose into pyruvate in the cytoplasm.
• Krebs Cycle: Occurs in mitochondria, generating ATP, CO2, and H2O.
• Energy from glucose breakdown is stored in ATP (adenosine triphosphate).

Types of Respiration

• Aerobic Respiration:

  • Uses oxygen.
  • Complete breakdown of glucose.
  • Produces CO2, H2O, and 38 ATP.
  • Occurs normally throughout the plant's life.

• Anaerobic Respiration:

  • Occurs temporarily in some plant parts, like seeds.
  • Breakdown of glucose to ethanol and CO2, yielding 2 ATP.
  • Common in microorganisms like bacteria and fungi.

Comparison with Burning

• Both processes release energy but differ in several ways:
  • Respiration is a cellular, enzyme-driven, multi-step process at body temperature.
  • Burning is a non-cellular, single-step process at high temperatures.
  • Burning releases all energy as heat and light, while respiration yields ATP and some heat.

Plant Respiration Mechanisms

• Every plant part, including leaves, stems, and roots, undergoes respiration.
• Oxygen enters through:
  • Stomata in leaves
  • Lenticels in stems
  • Root surfaces

Experiments in Plant Respiration

1. Oxygen Utilization:
   • Use germinating seeds to show oxygen consumption.
2. CO2 Production:
   • Use limewater to detect CO2 release from germinating seeds.
3. Heat Production:
   • Demonstrate heat release during germination with thermoflasks.
4. Anaerobic Respiration:
   • Use mercury to show anaerobic respiration in seeds.

Respiration vs. Photosynthesis

• Respiration breaks down glucose, releasing CO2, whereas photosynthesis builds glucose using CO2.
• Photosynthesis occurs in light; respiration occurs all the time.
• Photosynthesis results in weight gain; respiration results in weight loss.

Special Considerations

• Respiration in animals involves transport of gases via blood, unlike the diffusion in plants.
• In anaerobic conditions, plants produce ethanol, whereas animals produce lactic acid.

Key Takeaways

• ATP is the energy currency in cells.
• Respiration and photosynthesis are complementary processes.
• Gaseous exchange, energy production, and plant physiology are interrelated through respiration.

Questions for Review

1. Outline the chemical equation and steps involved in respiration.
2. List differences between aerobic and anaerobic respiration.
3. Name organisms that respire anaerobically.
4. Explain the role of stomata and lenticels in respiration.