Mass Transport Systems in Plants

Overview

• Plants transport sugars via translocation and water via transpiration.
• Photosynthesis occurs in leaves, producing sugars that need to be distributed for energy use or storage.

Translocation

• Conducted through phloem cells arranged end-to-end forming phloem tubes.
• Phloem cells have pores allowing movement of sap (water and sugar mixture).
• Sugars can move in any direction through phloem.
• Uses:
  • Immediate energy.
  • Storage for future energy use.

Transpiration

• Conducted through xylem tubes, which are dead cells forming a long hollow tube.
• Xylem transports water and mineral ions from roots to leaves.

Mechanism

• Transpiration stream: Evaporation of water from leaves pulls the water chain upward.
• Stomata must be open for CO2 intake, causing water to evaporate.

Factors Influencing Transpiration Rate

1. Light Intensity:
   • More light increases photosynthesis, opening more stomata and increasing transpiration.
   • At night, closed stomata lead to reduced transpiration.
2. Temperature:
   • Higher temperatures increase water molecule energy, leading to more evaporation.
3. Air Flow:
   • High air flow removes water molecules faster, maintaining a high concentration gradient and increasing transpiration.
4. Humidity:
   • High humidity decreases transpiration by reducing the concentration gradient.

Conclusion

• Transpiration and translocation are crucial processes for plant survival and function.
• Understanding these processes helps explain how plants manage water and nutrient distribution.

Additional Resources

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