CHAPTER 4 TRANSPORT IN PLANTS

CHAPTER 4
TRANSPORT IN

PLANTS

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4.1 VASCULAR TISSUES

The Necessity of Transport in Plants VASCULAR TISSUES

 Plants are multicellular organisms which are XYLEM PHLOEM
formed from cells that need water and
nutrients Transports water Transport organic
and mineral salts compounds which are
 The large and tall size of the plants creates absorbed by the synthesized by the
a total surface area that is insufficient for roots to the stems
the plant to absorb its basic needs from the leaves through
surroundings and leaves photosynthesis to the

 To overcome this problem, plants have stems and roots
vascular tissues to transport water, mineral
salts and nutrients to all the cells Plants which have a transport system are
known as vascular plants
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Non-vascular plants like alga and moss do
not have any transport system

Structural Adaptations Of Xylem Vessels And Tracheids To Transport
Water And Mineral Salts

Xylem Vessel
C1 : consists of dead cells at maturity which do not have cytoplasm
C2 : these cells are arranged longitudinally from end to end
F2 : to form a continuous tube to allow water flow from the roots to the leaves

C3 : the walls of the xylem vessel have uneven lignin thickening Xylem vessel
F3 : give strength to xylem vessels to prevent from collapsing due to the tension

force and pressure changes when water moves through it

Tracheid Vessel
C1 : the cell wall has a lignin thickening and

pits
F1 : to allow water movement to adjacent cells

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Structural Adaptations Of Sieve Tubes and Companion Cells To Transport of Organic
Substances

Phloem Tissues

 F : transport and distribute dissolved organic compounds such as sucrose,
amino acid and plant hormones to all parts of the plant

 C : Phloem is a living cell because it has cytoplasm

Xylem Phloem Sieve Tube
Companion cell
C1 : do not have nuclei, ribosome or vacuole
F1 : allows sucrose molecules to pass through sieve tubes easily
C2 : on both ends of the sieve tube, there is a sieve plate that has pores
F2 : allow the organic compound to flow from one sieve tube to the next
C3 : companion cells contain mitochondria
F3 : to provide energy in form of ATP to transport sucrose from leaf to the

sieve tube through active transport

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4.2 TRANSPORT OF WATER AND MINERAL SALTS

The Necessity of Water in Plants The Movement of Water and Mineral Salts

 For plants growth because water helps to move  Involved 3 processes:
mineral salts from the soil to the stems i. Transpirational pull :

 Water also helps in giving turgidity to plant cells so - produced when water that is evaporated from
that the plant remains fresh the stoma, pulls water from the leaves

ii. Capillary action:
- produced from adhesion and cohesion force of
water molecules which moves water upwards
in the stem against gravity

iii. Root pressure:
- moves water from the soil into the xylem
vessels of the root via osmosis

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How Does Water Move From The Soil To The Xylem Vessel????

 The water potential in the root hair
cells is lower compared to water in
the soil

 This is because the mineral ions are
actively pumped by the root hair cells
into the vacuole

 causing the cell sap of the root hair
have low water potential compared to
the soil

 Water from the soil diffused  This condition causes osmosis to  This causes root pressure to
into the root hair cells and continuously occur throughout the push water into the xylem
epidermal cells via osmosis cortex, endodermis and pericycle vessels of the root and then
 The high water potential in the root layers into the xylem vessels of the
hair cells causes the water to diffuse stem
from the root hair cells into the cortex
via osmosis

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How Does Water Move In the Xylem Vessels????

 For tall plants, root pressure cannot
transport water to the leaves,
especially the shoots

 S0, the movement of water molecule
in the xylem vessel is also helped by
the capillary action of xylem
produced by adhesion and cohesion
forces and also transpirational pull

 Adhesion and cohesion forces
produce a pulling force which
continuously moves water in the
xylem vessel

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How Does Water Move In the Xylem Vessels????

 When transpiration process happens, water diffuse
out as water vapour from the spaces between the
cells to the surroundings through opened stoma

 Spongy mesophyll cells lose water and they have low
water potential towards adjacent cells

 Water molecules diffuse from neighbouring cells via
spongy mesophyll cells by osmosis

 This movement produces a force called
transpirational pull that pulls water molecules in the
xylem vessels of the leaves to the outside of the
leaves

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Guttation in Plants

 Is a secretion of water droplets through a special
structure at the end of the leaf veins without
involving the stomata caused by a high root
pressure

 Guttation occurs when the root pressure and the
rate of transpiration is low

 Occurs at night and early morning when the air
humidity is high and the surrounding temperature is
low

 The root pressure formed pushes water to the
leaves and stems of the plant

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Comparison Between Guttation and Transpiration

GUTTATION TRANSPIRATION

SIMILARITIES

 Both processes occur through the leaf
 Both processes cause permanent water loss from the plant

DIFFERENCES

Happens at night and early morning Happens on hot and windy days

Only happens in herbaceous plants happens in all plants

Water released in the form of water droplets Water released as water vapour

Water is released through a special structure at the end of the leaf veins Water is released through stomata opening and closing

Guttation happens when root pressure is high Controlled by the stomatal opening and closing

Releases water that is rich in minerals PREPARED BY CIKGU HUSRReITlAeMaRsSeMs TpRuANreSKRwIAaNter

The Condition of Plants That Do Not Undergo Transpiration and Guttation

EFFECTS TOWARDS PLANTS THAT DO NOT EFFECTS TOWARDS PLANTS THAT DO NOT
UNDERGO GUTTATION UNDERGO TRANSPIRATION

 Root pressure cannot be maintained  Optimum temperature of plants cannot be
 Water absorption by root hair cells is distrupted maintained

in a surrounding with high relative humidity  Increase in temperature can denature enzymes
 Plant waste substances cannot be eliminated and distrupt biochemical processes such as
 The leaf vein pressure becomes high and causes photosynthesis and respiration

the leaf vein to burst. This leads to the leaves  Mineral ions such as potassium ion cannot be
being exposed to pathogen and eventually fall transported from the roots to the leaves for
photosynthesis

 Water transport throughout the plants will be
distrupted and causing the plants to wilt

 Plants can die in the long run

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4.3 TRANSLOCATION

D : Is a process of transporting organic substances such as sucrose, amino
acids and hormones in the phloem from the leaves to other parts of the plant
such as the roots and stem

THE NECESSITY OF TRANSLOCATION IN PLANTS
i. Transporting photosynthetic products from the leaves to

other parts of the plant for growth and respiration such
as roots, fruits, tip of shoots or developing flower
ii. Transports excess photosynthetic products to other
parts of the plants such as rhizomes, tubers and bulbs

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Pathways of Translocation in Plants

Sucrose is actively Transpiration pulls water along
transported into the sieve the xylem vessels against the
tube direction of gravitational pull

• The transport of sucrose into The high water potential in the
the sieve tube through the phloem causes the water to
companion cell from the leaf diffuse in order for it to
cells reduces the water return into the xylem by
potential in the sieve tube osmosis

• This causes water to diffuse
from the xylem into the sieve
tube via osmosis

The water diffusion increases The increase in the hydrostatic The phloem sap (sucrose) is
the hydrostatic pressure in the pressure causes the phloem transported from the sieve
sieve tube sap to be pushed along the tube to other parts such as
sieve tube to other organs of stem, roots, shoot, fruits and
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4.4 PHYTOREMEDIATION

D : Is one of the treatment methods which uses plants for the purpose of
degradation, extraction or elimination of pollute substances from soil and water

THE IMPORTANT OF PHYTOREMEDIATION
i. One of the alternatives in waste water treatment by eliminating heavy

metals and also trapping harmful nutrients and microorganisms

 Phytoremediation treatment uses aquatic plants that can absorb heavy metals and
nutrients contained in waste water

 Example of plants: Eichhornia crassipes (water hyacinth)- has long roots which can

accumulate heavy metals such as copper and lead in water

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The Uses of Phytoremediation In Life

Sunflower
 used for remediation of soil polluted by the explosion of nuclear plant in

Chernobyl, Russia
 Act as a hyperaccumulator which can eliminate heavy metals such as zinc,

chromium, copper, lead and nickel and also radioactive substances such as
caesium and strontium

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The Uses of Phytoremediation In Life

Pistia stratiotes (water lettuce plant)

 used to treat waste water in a waste plant
 Pistia stratiotes which has a fast growth rate, can accumulate

heavy metals and absorb nutrients in the waste plant

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The Uses of Phytoremediation In Life

Water spinach
 The roots of ground water spinach are able to absorb mercury from the

soil whereas the roots of river water spinach are able to absorb heavy
metals such as cadmium from the water

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