DOL 21.2 The Vascular System

Water moves up from a plant’s roots through cells in the xylem that

• act like tiny pumps.

• carry sugar to the roots.

• have matured and died.

• have no cell walls.

The cohesion-tension theory proposes that water rises through plants because of

• metabolic energy expended by the plant.

• the physical properties of water. (absorption, cohesion and adhesion, transpiration)

• pressure changes between sources and sinks.

• transpiration from roots.

Water vapor escapes from plants by the process of

• capillary action.

• transpiration.

• cohesion.

• adhesion.

Phloem tissue is made up mainly of

• xylem cells and stomata.

• dead cells and sugar sinks.

• vessel elements and tracheids.

• sieve tube elements and companion cells.

What does the pressure-flow model explain?

• how pressure is kept the same throughout a plant

• how water moves through a plant

• how sugars are produced by photosynthesis

• how sugars move through a plant