- Plants take water up through the roots. The water passes through the plant to the leaves. In the leaves the water evaporates from the leaf cells and the water vapour diffuses out through the sotmata
- The movement of water through the plant is called the 'transpiration stream'.
- The plant could dehydrate of the rate of evaporation in the leaves is greater than the water uptake by the roots
- Evaporation is more rapid in hot, dry, windy or bright conditions.
- The guard cells can close to prevent excessive water loss. Wilting of the whole plant can also reduce water loss. The leaves collapse and hang down, which reduces the surface area