Plant Transport

1. Plant Transport
Reason for transport system
Transport system in plants
Adaptations of xylem tissues
Adaptations of phloem tissues
Absorption of root hair cells
Water movement processes
Transpiration pull
Rate of transpiration

2. 1. Reason for transport system
Unicellular organisms
They can transport materials like oxygen and urea in and
out of their bodies by diffusion or osmosis easily.
Multicellular organisms
Most of the cells inside the organisms are too far from the
surface of their bodies and diffusion and osmosis are too
slow to be relied on.
A transportation system is required for food and oxygen to
be brought efficiently from one place to another.
Diffusion and osmosis would take place between the
transport system and the cells.

3. 2. Transport system in plants
Xylem and Phloem tissues
Xylems transport water and minerals salts (nitrates) from
roots to leaves in a unidirectional motion
Phloems transport organic products (sucrose) from the
leaves to all parts of the plant in a bidirectional motion
Vascular bundles
Xylem and Phloem tissues are arranged in vascular
bundles. A cambium separates the xylems and phloems.
The cambium undergoes division to produce new xylems
and phloems.

4. 2. Diagrams of the system
Sites of xylem and
phloem tissues

5. 3. Functions of Xylem tissues
Support
Consists of lignin to provide the plant with support
Transport of water and nitrates
Conducts water and dissolved mineral salts from the roots
to all other parts of the plant

6. 3. Formation of Xylem tubes
The xylem cells die when they mature. The cross
walls and cell contents will break down.
A hollow lumen will be left. There is no obstruction
to the flow of water.
The walls of the cells are thickened with lignin. It
causes the walls to be rigid, supporting the plant.

7. 3. Adaptations of Xylem tissues
Absence cross walls
Maintains a continuous
lumen
Protoplasm disintegrate
Allows water to move
efficiently
Dead empty tube
Maintains a continuous
lumen
Lignified walls
Walls are rigid
Xylem will not collapse
Supports the plant

8. 4. Adaptations of Phloem tissues
Bi-directional sucrose
flow
Food can be transported
to all parts of the plant
Cross walls perforated
by sieve tubes
Single row of thin
elongated walls with
minute pores
Living cells to conduct
the food in the tube
Companion cell present
Consists of protoplasm
and mitochondria
Assists sieve tubes in
transport of food
Provides energy
required for active
transport
When dead, sieve
elements will die off

9. 5. Root hair cells
Plants absorb water and minerals from the soil
through the root hairs.
Root hair cells absorb water and nitrates from the
soil efficiently.
They help to hold the plant more firmly to the
ground.

10. 5. Adaptations of root hairs
Finger-like extensions
Increases surface area to
volume ratio
To absorb water and
mineral salts at a faster
rate
Lower water potential
Allow osmosis and
diffusion of nitrates to
take place
Large vacuole
To absorb as much
water as it can hold
Is a living cell
Carries out respiration
This provides energy for
active transport to take
place when water
potential is lower in the
soil

11. 5. Osmosis in the Root cells
The soil particles have a higher water potential than the
vacuole of the root hair cell.
Water and nitrates diffuse from the soil particles to the root
hair cell.
The root hair cell becomes more dilute than the surrounding
cortex cells. Water and nitrates diffuse from the root hair cell
to the cortex cells by osmosis.
Water diffuses from one cell to another until water eventually
enters the xylem tubes
Intake of water in the roots, the root hair cells become turgid.
A pressure is thus generated. This pressure is called root
pressure. This forces water up the xylem tissues.

12. 6. Forces causing water movement
Root pressure
Produced by the continuous movement of water through
the root hair cells
Pushes water up the xylem
Transpiration pull
Produced by the evaporation of water from the leaves
Pulls water up the xylem
Capillary action
Produced by the conduction of water by the xylem
through its continuous lumen
Pushes water up narrow xylem vessels

13. 7. Transpiration in the stomata
In the stem xylem, water is pulled up the stem by
transpiration pull.
Osmosis continues through the leaf cells and water is
eventually drawn in from the xylem vessels in the stem.
As the water evaporates, the water potential of cell sap
decreases. It draws water from the lower cells by osmosis.
Water evaporates from the surfaces of leaf cells into air
spaces.
Water vapour from the air spaces diffuses through the stoma
and into the atmosphere.

14. 7. Transpiration pull of plants
Plants absorb a large amount of water, but make use of only a
small portion of the water.
A large portion of water is lost by evaporation of water
through the stomata of the leaves. This process is called
transpiration.
Transpiration is the loss of water vapour mainly from the
stomata of the leaves.
As water evaporates from the leaves, more is drawn up
through the plant to replace it due to cohesion forces
between water molecules in the xylem tissues.
A pulling force called the transpiration pull is formed.

15. 7. Importance of Transpiration pull
Transpiration pull is the transport of water and
mineral salts or nitrate ions from the soil to the
leaves.
Ensures a constant flow of water to be taken from
the soil to the leaves.
Enables photosynthesis to occur.

16. 8. Rate of transpiration increase
Humidity of air
Low
Dryness of air
High
Temperature of air
High
Speed of wind
High
Light intensity
High

17. 8. Light intensity
Presence of light
Photosynthesis occurs.
Cell sap in guard cells has higher concentration of glucose.
Water enters the guard cells by osmosis causing guard
cells to become turgid.
Stomata opens and transpiration increases.
Absence of light
No photosynthesis occurs.
Plant loses water, guard cells flaccid.
Stomata closes and transpiration decreases.