The pull from above

The idea

Transpiration is the loss of water as vapour from the aerial parts of a plant; evaporation from leaf cells creates a suction that pulls water up through the xylem from the roots.

Wet washing

Wet clothes dry in the sun because water evaporates from them.

Plants also lose water as vapour. Where do you think the water in a tall tree is pulled from?

• Up from the roots
• Down from the clouds
• Sideways from the air

The suction

Press Next step.

Pulled from the top

Water evaporates from the cells of the leaves and leaves the plant as vapour. This loss of water from the aerial parts is transpiration. Each loss creates a suction that pulls water up from the xylem of the roots. The water lost through the stomata is replaced by water from the xylem vessels in the leaf, as long as the plant has enough water.

Transpiration is the loss of water as vapour from the aerial parts of a plant; evaporation from leaf cells creates a suction that pulls water up through the xylem from the roots.

Notes

Transpiration: water lost as vapour from the aerial parts; evaporation from leaf cells creates a suction that pulls water up the xylem from the roots.

Check yourself

What is transpiration?

What creates the suction that pulls water up in the xylem?

By what is the water lost through the stomata replaced?

Which parts of a plant lose water as vapour in transpiration?

• The loss of water as vapour from the aerial parts of a plant — correct. Yes!
• The uptake of ions by root cells. That is how the root pressure is created.
• The movement of sugar through the phloem. The transport of soluble products of photosynthesis is called translocation.
• Active uptake of ions by root cells. This leads to root pressure, which pushes water up from below.
• Evaporation of water from leaf cells — correct. Yes!
• ATP moving sucrose into the phloem. That is how translocation in the phloem is driven by energy.
• Water from the phloem sieve tubes. Phloem transports the products of photosynthesis.
• Water made in the stomata. Stomata are tiny pores; the water is replaced by water from the xylem.
• Water from the xylem vessels in the leaf — correct. Yes!
• The aerial parts — correct. Yes!
• The parts in the soil. Transpiration is the loss of water in the form of vapour from the aerial parts.
• Only the root cells. Roots take up water from the soil; transpiration happens from the aerial parts.