Plant Mass Transport Systems

Overview

• Purpose: Discuss how plants transport sugars and water.
• Key Processes:
  • Translocation: Movement of sugars.
  • Transpiration: Movement of water.

Translocation

• Definition: Transport of sugars produced by photosynthesis in the leaves to other parts of the plant.
• Mechanism:
  • Achieved primarily through phloem cells.
  • Phloem cells are arranged end-to-end forming phloem tubes.
  • Phloem tubes have pores for the movement of "celsa", a water and sugar mix.
  • Sugars are transported for energy use or storage.
  • Phloem can transport substances in both directions (up/down the plant).

Transpiration

• Definition: Movement of water and mineral ions from roots to leaves.
• Mechanism:
  • Achieved through xylem tubes, consisting of dead xylem cells with no ends.
  • Xylem tubes are hollow and strengthened with lignin.
  • Driven by evaporation of water from leaves’ stomata.
  • Evaporation pulls the "chain" of water molecules up the plant, known as the transpiration stream.

Factors Affecting Transpiration Rate

1. Light Intensity

   • More light = more photosynthesis = more stomata open = higher transpiration rate.
   • At night: Stomata closed, reducing transpiration.

2. Temperature

   • Higher temperature increases particles’ energy, promoting evaporation and a higher transpiration rate.

3. Air Flow

   • High airflow (windy conditions) increases transpiration by maintaining a high concentration gradient outside the leaf.

4. Humidity

   • High humidity decreases transpiration as moist air reduces the concentration gradient.

Conclusion

• Translocation and transpiration are crucial for plant survival, ensuring distribution of nutrients and water.
• Various environmental factors significantly influence these processes.

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