Transcript Distribution of vascular tissue in dicotyledonous plant

Transport in flowering plants
is provided by
vascular
tissue
xylem
phloem
transport
• water
• substances
dissolved in water
transport
• organic nutrients
Distribution of vascular tissue in
dicotyledonous plant
leaf
leaf
vein
xylem
phloem
midrib
vein
Distribution of vascular tissue in
dicotyledonous plant
xylem
phloem
stem
Vascular bundle
cortex
Distribution of vascular tissue in
dicotyledonous plant
root
phloem
cortex
xylem
Xylem cells
xylem tissue is made up of
xylem vessels
• thick cellulose cell
walls with lignin
• dead, hollow cells
• no cross wall
between cells
• provide support to
plant other than
transport
xylem vessels
Phloem cells
phloem tissue is made up of
sieve tubes and companion cells
sieve tube
1. sieve tubes
• living cylindrical cells
(cytoplasm,no nucleus)
• thin cellulose cell walls with no lignin
• joining end to end to
form long tube
• substances can pass
from cell to cell
through sieve plates
phloem cells
Phloem cells
phloem tissue made up of
sieve tubes and companion cells
2. companion cells
companion cell
• narrow cell with a nucleus
/ numerous organelles
• support the metabolic
activities of the sieve
tubes
phloem cells
The plant wilts
The cells of leaves
lack water
• Turgidity of cells provides support to plants
Osmosis in plant cells
• In a solution with higher
water potential
– water moves in by
osmosis
– cell turgid  fully turgid
• In a solution with lower
water potential
– water moves out by
osmosis
– cell flaccid  plasmolyzed
Water Balance in plant
• evaporation
• transpiration
• absorption
by root
Transpiration in plants
What is transpiration?
• loss of water vapour from surfaces of
plants due to evaporation
Where does transpiration occur?
• stomata ( > 90% )
• lenticels ( < 10%)
• waxy cuticle
(very small amount)
Transpiration through stomata consists of 2 steps :
1 Water evaporates
into the air space
2 Water diffuses out
through the stoma
water lost from leaves
Water is replaced by :
2 As a result, cells draw
water from the xylem,
pulling water up the
plant.
1 Water is lost from the
cell surface (cell wall),
which is replaced by
the water in the cell.
Each cell then pulls
water from its
neighbouring cells.
through cell wall
water lost from leaves
through cytoplasm
and vacuoles
Light intensity
light intensity 
– more CO2 for
photosynthesis
 stomata open more widely
vapour 
 more water vapour diffuses
out
 transpiration rate 
transpiration rate
 SA for diffusion of water
light intensity
 light intensity   Temperature
Temperature
temperature 
 rate of evaporation 
 rate of diffusion of water
vapour 
 more water vapour diffuses
out
 transpiration rate 
transpiration rate
 diffusion gradient 
15 20 25 30
temperature (oC)
Relative humidity
 lower concentration
of water vapour in
the surrounding air
 diffusion gradient
of water vapour 
 more water diffuses
out
 transpiration rate 
transpiration rate
relative humidity 
0
20
40
60 80
relative humidity of
atmosphere (%)
100
Air movement
 remove water vapour
accumulating near
the leaf surface
 diffusion gradient
of water vapour 
 rate of diffusion 
 more water vapour
diffuses out
 transpiration rate 
transpiration rate
air movement 
0
8
16
24
wind velocity (km/h) (air
movement)
To Measure the Rate of
Transpiration by Using a
Simple Potometer
graduated
capillary tube
leafy shoot
reservoir
tap
air/water
meniscus
What are the environmental conditions under which
transpiration occurs quickly ?
Ans: It is under dry, warm and windy conditions.
graduated
capillary tube
leafy shoot
reservoir
tap
air/water
meniscus
Does this apparatus give you an accurate measurement of
the rate of transpiration ?
Ans: In
No.addition,
It is because
it is too
it only
small
measures
to fit thethe
whole
rateroot
of water
system
uptake
and
thisby
may
theaffect
leafy shoot
the rate
… of water uptake.
graduated
capillary tube
leafy shoot
reservoir
tap
air/water
meniscus
Sometimes you may introduce an air bubble into the
capillary tube. State the advantage of this method.
Ans: Movement of the air bubble is easier to observe
than that of air/water meniscus.
graduated
capillary tube
leafy shoot
reservoir
tap
air/water
meniscus
Sometimes you may introduce an air bubble into the
capillary tube. State the disadvantage of this method.
Ans: Friction between the capillary wall and the bubble
may affect the movement of bubble.
To Measure the rate of
water uptake and water
loss of a plant using a
weight potometer
Change in volume
in burette
V1
= (V2 – V1)cm3
= amount of water
uptake
V2
Change in weight
of the whole set-up
= (W1 – W2)g
W1
W2
24
hours
= amount of water
loss
Rate of water uptake
V1
= (V2 – V1) / 24 cm3/hr
V2
Water
retained
Photosynthesis /
new cells
1cm3
water
= (W1 – W2) / 24 g/hr
Rate of water loss
>
=
1g
water
Rate of water loss
W1
W2
24
hours
Rate of water
uptake
Concept diagram
Transport
in flowering plants
provided by
consist of
xylem
carries
water
phloem
carries
organic
nutrients
vascular
tissues
Transport of water and mineral salts
Xylem vessels transport – water
– mineral salts
water forms a
by transpiration pull
continuous
stream inside
water drawn
out of xylem
vessels to
replace
water loss
through leaf
transpiration
water in
xylem
vessels
is moved
up as
plants
transpire
minerals and
other
substances
dissolved in
water can be
transported
up the plant
Transport of organic nutrients
Phloem transport - organic nutrients
bud
through
sieve
plates
by
translocation
moving up to
growing part
moving down
to growing
fruit and root
for storage
organic
nutrients
made by
photosynthesis
water and minerals
absorbed by roots