Transport System in Plants
Prepared By: Faiz Abdullah
Transport System in Flowering
Flowering plants have a system of vessels that runs up and down
the plants carrying materials.
These vessels are called transport or vascular tissues.
YOU SHOULD KNOW TWO TYPES OF TRANSPORT
O Level question:
WHAT IS THE DIFFERENCE
BETWEEN XYLEM AND PHLOEM
XYLEM -- Function
FROM roots to stems to leaves.
II. Provide for the stem.
STRUCTURE & ADAPTATION
Consists mainly of xylem
vessels (long hollow tube)
Made up of many DEAD
Inner walls of the xylem vessels
are STRENGTHENED by
LIGNIN structural or
Has empty lumen without
protoplasm or cross walls.
Narrow lumen for capillary
action (not the same as
Transports manufactured food
(sucrose+amino acid) from leaves
to other parts of plant.
Consists of sieve tubes and
Sieve tube consists of columns of
elongated, thin walled living cells
called sieve tube cells/elements.
They have cross walls with many
holes or pores sieve plates
Each sieve tube has a companion
Companion cells have many
mitochondria provide energy
needed to load sugars from
mesophyll cells into sieve tubes
by active transport.
Sieve pores allow rapid flow of
manufactured food through sieve
The root is divided into several regions:
The root cap: located at the tip of the root. root
during growth through the soil.
Zone of cell multiplication/division: zone
Zone of elongation: The region where newly divided cells
elongate of root.
Zone of maturation: consists of root hairs, which increases
surface area for rapid and efficient uptake of water and salts
+ Transverse section of the
Take note of the labels
Vascular tissue in stem:
In dicotyledonous stem:
- Xylem and Phloem grouped together vascular bundle
- Vascular bundles are arranged in a ring around a central
- Phloem lies outside the xylem with a tissue in between
- Region between vascular bundles and the epidermis cortex
- Stem is covered by a layer of cells epidermis
Vascular tissues in a stem
• Cambium cells can divide and differentiate to form new
xylem and phloem tissues thickening the stem
• Cortex and pith serve to store up food substances such
• Epidermal cells are covered by a waxy, waterproof
cuticle that greatly reduces evaporation of water from
ENTRY OF WATER INTO
FROM ROOT STEM
To understand the movement of
We need to know how
PROPERTIES OF WATER
Water molecules are attracted to
one another by a force
Water tends to stick to the inner
surface of the walls of xylem
1) Movement of water into root hairs:
Movement of substances
OSMOSIS water from the soil move into the root hairs via osmosis.
Diffusion: Ions diffuse from a high concentration to a low
Active transport: minerals, such as Mg and N, which are in LOWER
concentrations in SOIL, enter the root cell via active transport
OSMOSIS FOR WATER ONLY
FOLLOWS CONCENTRATION GRADIENT
NO NEED ENERGY
DIFFUSION FOLLOWS CONCENTRATION GRADIENT
ACTIVE TRANSPORT NEEDS ENERGY (ATP)
AGAINST CONCENTRATION GRADIENT
1) Movement of water into root hairs:
a) Root hair is long and narrow increase surface area to
absorb more water and mineral salts by root hair cell
b) Cell surface membrane prevents cell sap (vacuole) from
leaking out. Also, Cell sap has lower water potential.
c) Root hair is living can provide energy for active transport
1) Movement of water into root hairs
Once water has entered a root hair, it passes from one cell to
another by Osmosis.
This goes on and on and on……..and on….until the water
reaches the xylem
At the same time, ions diffuse inwards through the cells of the
root until they reach the xylem
2) Root pressure (Guttation)
At night, mineral ions are actively transported into the xylem
This lowers the water potential in the xylem vessel.
Therefore, water passes from the living cells into the xylem by
osmosis and flows upwards root pressure
Guttation stops when transpiration begins
3) Capillary action
When water reaches the xylem vessel,
Its NARROW LUMEN allows water to move up the stem process known
3) Movement of water through the
Mesophyll cells evaporate large quantities of water into the
intercellular air spaces
Water vapor diffuses out of the leaves through the
Small amount of water is lost through the waxy CUTICLE
Enables water to move up the stem to the plants:
water can be used for photosynthesis and keep the cells turgid
(help leaves spread out widely to trap more light)
Evaporation of water cools the plant.
Enables plant to obtain mineral salts.
Why do you think transpiration
can help the plant?
Transpiration- features that
facilitate water loss
(a) Mesophyll cells with wet surfaces and large total surface area
(b) Large intercellular spaces in the leaf
a) Greater number in stomata
b) Stomata exposed directly to sunlight or remain open
Environmental factors that affect
② Air Humidity
④ Light intensity
⑤ Carbon dioxide concentration
WHEN? And WHY?
Wilting occurs when:
RATE OF TRANSPIRATION EXCEEDS RATE OF ABSORBTION
Cells lose their turgidity
Cells become flaccid
Water becomes a limiting factor.
Wilting causes a decrease in the rate of photosynthesis
Water is getting less
Wilting makes the leaves fold less area exposed to sunlight
The greater the size of stomatal opening, the greater the water
+ The transport or movement of
food substances in the
Investigation: to show water travels up the stem in the xylem
1. Set up the apparatus as shown.
2. Allow the plant to stand immersed in the red food dye for 3-4
3. Observe the color change in the stem
4. Cut thin transverse section of the stem
5. Observe under a microscope
The red dye will appear in the stem and leaves.
Xylem tissue has been stained red