B5: TransportationTransport in Plants

State the functions of xylem and phloem Flowering plants have two separate transport

systems: xylem and phloem. These tissues are found throughout the plant

body in roots, stems and leaves, Xylem vessels transport water and mineral ions

from the roots up the stem to the leaves. Roots absorb water and mineral ions from the soil. These travel in the xylem upwards in the stem to

the leaves, flowers and fruits. This is one-directional movement: from roots, via

the stem, to the leaves.Water movement in plants

Water transport

State the functions of xylem and phloem Phloem vessels transport sucrose, amino acids

and hormones to other parts of the plant. Sucrose is a soluble complex sugar Sucrose is made from the sugars made in

photosynthesis and from the starch stored in roots and stems.

Substances are moved in two directions in the phloem: downwards from leaves to roots upwards from leaves to flowers, fruits and buds Upwards from storage organs to new stems and leaves.

Phloem loading video

Plant tissue animation Water

movement animation

Inside a root

Inside a stem

Sink and source

Up the stem

Identify root hair cells and state their functions Roots have 2 functions:

Anchor the plant in the soil Take up water and mineral salts

Root hairs are microscopic Water passes into the root hair from the soil via osmosis. This process continues through all the cells until the

water reaches the xylem. The xylem transports the water up the stem.

Structure of root hairs: Long and thin with a large surface area.

Absorption by roots

Transpiration The evaporation of water

from the leaves and the loss of water vapour to the atmosphere. Water only diffuses out of

the leaf when the stomata are open.

The flow of water up the stem relies on: Cohesion of water

molecules to each other Adhesion of water

molecules to the xylem

Factors affecting transpiration

Use your textbook p93 to summarise the factors that will affect the rate of transpiration in a plant (draw graphs if appropriate) Light Humidity Temperature Wind

Page 98 – 99 complete the exam-style questions: 1 - 7