Summary of "GCSE Biology Revision "Transpiration""

Scientific concepts & nature phenomena presented

Ongoing evaporation of water from the surfaces of leaves.
Water vapor forms from cells within the leaf, diffuses through internal air spaces (notably the spongy mesophyll), and escapes through stomata.

The linked movement of water from xylem into the leaf to replace water lost via transpiration.
Water is drawn up from root hair cells through xylem vessels to the leaves.

Palisade mesophyll: site of photosynthesis.
Xylem: transports water and dissolved mineral ions from roots to leaves.
Spongy mesophyll (air spaces): pathway for water vapor diffusion before exiting via stomata.

Higher temperature → higher transpiration rate
- Higher temperature increases the evaporation process.
Drier air (low humidity) → higher transpiration rate
- Lower humidity increases the evaporation gradient.
Windy conditions → higher transpiration rate
- Wind removes water vapor near the leaf surface, allowing more evaporation.
Higher light intensity → higher transpiration rate
- Increased light promotes photosynthesis, which leads to stomata opening.
- This allows carbon dioxide entry and also increases water vapor loss.

The plant may close stomata to reduce water loss.
This also means less CO₂ can enter, so photosynthesis can’t proceed as effectively.

Brings water to the leaves (needed for photosynthesis).
Transports dissolved mineral ions (e.g., magnesium) via the transpiration stream.
Cools the leaf via evaporative water loss, especially important in warm weather.