Food movement needs energy

The idea

Unlike xylem transport, largely explained by physical forces, phloem translocation uses energy: ATP moves sucrose into phloem, raising osmotic pressure so water enters, and this pressure moves material to tissues with less pressure, as the plant needs.

Two kinds of movement

Water climbs the xylem mostly because of simple physical forces.

Do you think food in the phloem moves in the same simple way?

• No, it uses energy
• Yes, with no energy
• It does not move

Loading and pushing

Press Next step.

Energy for the food route

Water in the xylem moves mainly because of simple physical forces. Food in the phloem needs energy. Using energy from ATP, sucrose is moved into the phloem. That raises the osmotic pressure there, and water moves in. The pressure then pushes the material to tissues that have less pressure, so the plant can send food where it is needed.

Unlike xylem transport, largely explained by physical forces, phloem translocation uses energy: ATP moves sucrose into phloem, raising osmotic pressure so water enters, and this pressure moves material to tissues with less pressure, as the plant needs.

Notes

Phloem translocation uses energy: ATP moves sucrose in, the osmotic pressure rises, water enters, and the pressure moves material to tissues with less pressure, as the plant needs.

Check yourself

Where does the energy for loading sucrose into the phloem come from?

What happens after sucrose is moved into the phloem?

The material in the phloem moves to tissues that have ...

In spring, the sugar stored in root or stem tissue is moved to the ...

• ATP — correct. Yes!
• Simple physical forces alone. This explains transport in the xylem; translocation in the phloem uses energy.
• Root pressure. Root pressure is the push from water entering the root xylem.
• Water moves out of the phloem. The increased osmotic pressure causes water to move into the phloem tissue.
• The osmotic pressure increases and water moves into the tissue — correct. Yes!
• The osmotic pressure falls. Moving sucrose in increases the osmotic pressure of the tissue.
• more pressure. The pressure moves the material to tissues which have less pressure.
• no cells. The material is delivered to tissues that need it, according to the plant's needs.
• less pressure — correct. Yes!
• buds, which need energy to grow — correct. Yes!
• stomata. Stomata are tiny pores on the leaf surface.
• soil. Sugar is carried to tissues which need it, such as buds, not into the soil.