1. The document discusses transport in plants, including translocation, transpiration, and the pathway of water movement. 2. Translocation is the transport of dissolved organic foods by the phloem. Transpiration is the loss of water vapor through stomata, cuticle, and lenticels. 3. Water moves through the xylem via root pressure, capillarity, and transpirational pull from the roots to the leaves. External factors like temperature, light, and humidity affect the rate of transpiration.

1. BIOLOGY FORM 5 CHAPTER 1 : TRANSPORT

2. LEARNING
OUTCOMES
• To state what translocation is.
• To explain the importance of
translocation in plants.
• To describe the process of transpiration.
• To explain the importance of
transpiration.
• To describe the pathway of water from
the soil to the leaves.
• To state external conditions affecting
transpiration

3. TR A N S L O C A TI
ON
• T h e t r a n s p o r t o f d is s o l v e d
o r g a n ic f o o d s u b s t a n c e s b y
t h e p h l o e m.
IM P O R T A N C E O F
T R A N S L O C A T IO N
• Ensures a plant’s survival
• Organic food molecules can be transported :
– To the growing regions in the plant for growth &
development
– To the plant cells for metabolism
– Downwards from the leaves to the storage organs such

6. T R A N S P IR A T
IO N
• The loss of water as water vapour from a living
plant to the atmosphere due to evaporation.
• M os t of th e wate r is los t th rou gh th e
stomata of le ave s .
• A s m all am ou nt is los t th rou gh th e cuticle
or th rou gh th e lenticels in wood y s te m

7. • T hree main sites of transpiration are :
– S T OM A T A – 90% of transpiration takes place
through minute pores on leaves called stomata
– C UT I C L E – 10% of transpiration takes place
through the cuticle. The amount of water loss
varies with the thickness of the waxy cuticle
– L E NT I C E L S – small pores in the stem which
allow gaseous exchange. Only small amounts of
water are lost through the lenticels.

8. • Transpiration occurs mainly during the day
when the stomata are opened.
• Heat from the sun causes the water to
evaporate from the walls of the spongy
mesophyll cells.
• The water vapour accumulates in the
substomatal air chambers before diffusing
from the plant through the open stomata

9. • Water move into the mesophyll
cells by osmosis from the
adjacent cell
• Water flows from the xylem
vessels along a chain of cells to
the outermost mesophyll cell.
• Water is pulled through the xylem
vessels from the root to the

14. T h e I mp o r t a n c e o f
T r a n s p ir a t io n
• Creates a transpirational pull that pulls
water & dissolved mineral ions from the
root to the leaves.
• Water supplied to the plant is used for
photosynthesis & cell metabolism. Mineral
ions is used for cell activities & growth &
development of the plant.

15. • Water keeps the cell turgid  give support
to leaves & young stems (herbaceous
plants).
• To keep the plant cool, an important effect
particularly in hot condition.
• Water evaporates from the plants to the
atmosphere faster than it can be absorbed
from the soil, it is withdrawn from the plant
cells  flaccid – leading to wilting

17. P A TH WA Y O F WA TE R
F R O M T H E S O IL T O
TH E L E A VE S
• Water & mineral ions are absorbed by young
roots with thin epidermis. (osmotic forces +
active transport)
• The pressure of root hairs increases the
surface area for absorption.
• The cell sap in the root hair cell contains
sugars, amino acids, & minerals  more
concentrated than the surrounding dilute soil
solution.

18. • Wate r d iffu s e s into th e root ce lls b y
os m os is .
• Th e e ntry of wate r into th e root ce lls
d ilu te s its ce ll s ap .
• Th e ce ll s ap of th e ad j nt corte x
ace
ce ll is now m ore conce ntrate d 
wate r m ole cu le s d iffu s e into th e
ad j nt root ce ll.
ace

19. • The process continues & water is
transported from one root cell to
another by osmosis.
• In the cells of the endodermis,
mineral ions are actively pumped
from these cells into the solution in
the xylem vessels in the root.
• Solution in xylem more concentrated
 water enters xylem by osmosis.

20. • This process creates an upward force called
ROOT PRESSURE.
• Helps to push water in the xylem up to a
certain height in the plant.
• Root pressure alone is insufficient to force the
water to the top part of a tall tree.
• Need CAPILLARITY ACTION &
TRANSPIRATIONAL PULL.

21. G U T T A T IO N
• In small plants, root pressure can push
water all the way up the stem & out of
special pores called hydathodes at the
edges of leaves  Guttation
• Occurs on cool humid morning when the
air is too saturated for the water drops to
evaporate from the leaves.

23. TH E E XTE R N A L
C O N D IT IO N S
A F F E C T IN G T H E R A T E
O F T R A N S P IR A T IO N
• The external factors that affect the rate of
evaporation.
– Air movement
– Temperature
– Light intensity
– Relative humidity

24. A IR MOVE ME NT
• Movement of air carries away water
molecules that have diffused from the
leaves.
• The faster the air movement (wind speed)
the greater the rate of transpiration.
• When there is little air movement/ in still
air, water vapour diffusing out of the leaf
accumulates around the stomata.
• Decreases the concentration gradient of
water, the transpiration rate reduces.

25. TE M P E R A TU R E
• A rise in temperature increases the kinetic
energy of water molecules & increase the
rate of evaporation (transpiration).
• Lowers the relative humidity of the air 
increase the rate of transpiration.
• Temperature low, kinetic energy of water
molecules is decreased.
• Relative humidity of the air is higher 
decrease the rate of transpiration

26. L IG H T IN T E N S IT Y
• The light intensity increased, the
rate of evaporation increases.
• Light not effects evaporation but
causes the stomata to open 
increasing water loss from the
plant.
• At night @ dark, stomata close 

27. ð ^
• The rate of evaporation depends on the
difference in concentration of water molecules in
the sub-stomatal spaces & in the surrounding
atmosphere.
• The lower the relative humidity of the
surrounding atmosphere, the faster will the water
vapour escape from the stomata.
• High relative humidity reduces water loss.

28. ROOT
PRESSURE
• If a stem is cut just above ground level,
a considerable amount of sap will exude
from the cut stump, showing that there is
a force pushing water up the stem from
the roots.
• Its ROOT PRESSURE  The result of an
active process in which energy from ATP is
used.

29. ROOT
PRESSURE
• Root pressure alone is not strong enough to
drive water to the tops of tall trees at the
speeds achieved during a normal growing
season.

30. COHESION &
ADHESION OF
WATER
• COHESION = the force of attraction
between the same molecules
• The cohesive forces between water
molecules hold the continuous columns of
water together & when water transpires
from the leaf, the whole of the water
column moves up the xylem vessels.

31. • ADHESION = the force of attraction
between different molecules
• Water molecules tend to adhere to the
walls of the xylem vessels.
• The adhesive forces can support a
considerable mass of water.
• Cohesion + adhesion = capillarity (the rise
of water in a capillary tube).

32. O P E N IN G &
C L O S IN G O F
• Dicotyledonous O Mon the lower surface
S T leaves = A T A
• Monocotyledonous leaves = both the upper &
lower surfaces.
• Each stoma consists of a pair of kidney-shaped
guard cells surrounding a stomatal pore.

33. • A guard cell has a thinner elastic
outer cell wall & a thicker, less elastic
inner cell wall. It has a nucleus,
cytoplasm & chloroplasts.
• The opening & closing of the stomata
in the leaf controls the diffusion of
CO2 & O2 into & out of a leaf as well
as the rate of transpiration.

34. S TOMA TA L OPE NING
• DAY : photosynthesis occurs & CO2 level is low
in the leaf.
• Potassium ions (K+) diffuse from surrounding
epidermal subsidiary cells into the guard cells.
• In many plant species, starch stored in the guard
cell is converted into malate.
• The accumulation of K+ & malate ions increase
the osmotic pressure in the guard cell.

35. • Water enters by osmosis from surrounding
epidermal cells into the guard cells
• Two guard cells become turgid & curve
outward & the stoma opens.

36. S TO M A TA L
• NIGHT : no photosynthesis &G level
C L O S I N CO2
is high. Potassium ions move out of the
guard cells into the epidermal cells.
• Malate ions are converted to starch. The
osmotic pressure in the guard cells
decreases.
• Water diffuses out to the surrounding
epidermal cells by osmosis.

37. • Guard cells become flaccid & stoma
closes.
• The stomata also close, when there is
insufficient water supply & the
transpiration rate is high.

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