Download Module 2 Exchange and transport

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Diagram a
Diagram b
Diagram c
Module 2
Exchange and transport
1.2.13 Transport in plants-
Learning Objectives
Success Criteria
• Describe the structure and • Define xylem and phloem
(Grade D – C)
function of xylem vessels,
sieve tube elements and
• Describe the structure and
companion cells
function of a xylem and phloem
(Grade C –B)
• Compare the structure of xylem
and phloem, linking it to their
importance (Grade B – A)
How is xylem adapted for transportation?
Water and minerals travel in xylem
vessels.
Xylem vessels have thick cellulose
cell walls, strengthened &
waterproofed by lignin. The inside
of the cell is hollow. Xylem vessels
are dead cells. In some places
lignification is incomplete, there are
pores in the wall called
pits/bordered pits that allow water
to leave one vessel to the next
Xylem vessels transport water and
minerals from the roots to the
shoot and leaves. This transport
only occurs in one direction.
The thick walls of xylem cells also help support plants.
How is phloem adapted to transportation?
Phloem is made of columns of living
cells. They transport food, in the form
of sugars.
Sugars are carried from the leaves to
the growing and storage parts of the
plants. This movement takes place in
both directions.
Phloem cells consist of sieve tubes.
Cells are joined by small holes in the
cell wall at the end of each cell,
forming a continuous system. The end
cell walls are called sieve plates.
Companion cells carry out living
functions for both themselves and
sieve cells. Providing energy fro the
active transport of sugars