Why plants lose water

The idea

Transpiration helps absorb water and minerals and move them up from roots to leaves, and helps regulate temperature; root pressure matters more at night, while by day, with stomata open, transpiration pull is the major driving force.

Day and night

A plant moves water in the same xylem by day and by night.

Do you think the same force drives the water at all times?

• No, the main force changes
• Yes, always the same force
• There is no force

Day or night

Choose Day and Night and see which force matters more.

Many jobs, two forces

Transpiration helps the plant absorb water and minerals and lift them from the roots to the leaves. It also helps to regulate temperature. The root pressure matters more at night. By day, with the stomata open, the transpiration pull becomes the major driving force for the movement of water in the xylem.

Transpiration helps absorb water and minerals and move them up from roots to leaves, and helps regulate temperature; root pressure matters more at night, while by day, with stomata open, transpiration pull is the major driving force.

Notes

Transpiration helps absorb and lift water and minerals and regulate temperature; root pressure is more important at night, transpiration pull is the major force by day.

Check yourself

By day, with the stomata open, what is the major driving force for water in the xylem?

When is the effect of root pressure in moving water more important?

Besides absorbing and lifting water and minerals, what else does transpiration help with?

Transpiration helps in the absorption and upward movement of ...

• Root pressure. The effect of root pressure is more important at night.
• Transpiration pull — correct. Yes!
• Translocation in the phloem. Translocation is the transport of the soluble products of photosynthesis, not of water in the xylem.
• During the day. By day, with the stomata open, the transpiration pull is the major driving force.
• Only when the stomata are open. The book links the open stomata and the transpiration pull to the daytime.
• At night — correct. Yes!
• Regulating temperature — correct. Yes!
• Making sugar. Sugar is made from carbon dioxide and water in photosynthesis.
• Storing starch. Starch is the internal energy reserve that is stored by plants.
• starch from the leaves. Starch is stored; the products of photosynthesis move in the phloem.
• water and the minerals dissolved in it — correct. Yes!
• amino acids from the roots. Amino acids and other substances are moved by the phloem.