Transpiration (Cambridge O Level Biology)

• Water travels from the roots to the leaves of plants in the xylem vessels
• When water reaches the leaves it enters leaf mesophyll cells
• Water evaporates from the surface of leaf mesophyll cells into the air spaces in the leaf, from where it diffuses out of the leaf via the stomata in transpiration
• Transpiration can be defined as:

The loss of water vapour from the leaves of plants

Transpiration diagram

Water evaporates from the surface of leaf mesophyll cells and diffuses out of the stomata during transpiration

• Transpiration has several functions in plants:
  • Transporting mineral ions
  • Providing water to keep cells turgid in order to support the structure of the plant
  • Providing water to leaf cells for photosynthesis
  • Keeping the leaves cool