Transpiration (Cambridge (CIE) O Level Biology): Revision Note

Transpiration

• 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