title

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 Distribution of vascular tissue in dicotyledonous plantdicotyledonous plant

leafleaf

leaf vein

midrib vein

xylem

phloem

Distribution of vascular tissue in Distribution of vascular tissue in dicotyledonous plantdicotyledonous plant

xylem

phloem

stemstem

cortexVascular bundle

rootroot

Distribution of vascular tissue in Distribution of vascular tissue in dicotyledonous plantdicotyledonous plant

xylemphloem

cortex

Xylem cellsXylem cells

xylem vesselsxylem vessels

xylem tissue is made up of xylem vessels

• dead, hollow cells

• thick cellulose cell walls with lignin

• no cross wall between cells

• provide support to plant other than transport

phloem cellsphloem cells

Phloem cellsPhloem cells

phloem tissue is made up of sieve tubes and companion cells

• 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

1. sieve tubes sieve tube

phloem cellsphloem cells

Phloem cellsPhloem cells

phloem tissue made up of sieve tubes and companion cells

• narrow cell with a nucleus / numerous organelles

• support the metabolic activities of the sieve tubes

2. companion cells companion cell

The plant wilts

• Turgidity of cells provides support to plants

The cells of leaves lack water

Osmosis in plant cellsOsmosis 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

• evaporation• transpiration

• absorption by root

Water Balance in plant

lose

water

gain

wat

er

Transpiration in plantsTranspiration in plants

What is transpiration?

• loss of water vapour from surfaces of plants due to evaporation

Where does transpiration occur?Where does transpiration occur?

• stomata ( > 90% )

• lenticels ( < 10%)

• waxy cuticle (very small amount)

water lost from leaveswater lost from leaves

Transpiration through stomata consists of 2 steps :

1 Water evaporates into the air space

2 Water diffuses out through the stoma

water lost from leaveswater lost from leaves

Water is replaced by :

1 Water is lost from the cell surface (cell wall),

2 As a result, cells draw water from the xylem, pulling water up the plant.

which is replaced by the water in the cell. Each cell then pulls water from its neighbouring cells.

through cell wall

through cytoplasm and vacuoles

Light intensityLight intensity– more CO2 for

photosynthesislight intensity

more water vapour diffuses out

stomata

transpiration rate

open more widely

tra

nsp

iratio

n r

ate

light intensity

SA for diffusion of water

vapour

light intensity Temperature

TemperatureTemperature

temperature

more water vapour diffuses out

rate of evaporation

transpiration rate

rate of diffusion of water vapour

temperature (oC)tr

ans

pira

tion

ra

te302515 20

diffusion gradient

diffusion gradient

of water vapour

concentration of water vapour in the surrounding air

more water diffuses out

Relative humidityRelative humidity

relative humidity

lower

relative humidity of atmosphere (%)

tra

nsp

iratio

n r

ate

0 20 40 60 80 100 transpiration rate

remove water vapour accumulating near the leaf surface diffusion gradient

of water vapour

Air movementAir movement

more

air movement

water vapour diffuses out

transpiration rate

more

rate of diffusion

wind velocity (km/h) (air movement)

tra

nsp

iratio

n r

ate

0 8 16 24

To Measure the Rate of To Measure the Rate of Transpiration by Using Transpiration by Using

a Simple Potometera Simple Potometer

What are the environmental conditions What are the environmental conditions under which transpiration occurs quickly ?under which transpiration occurs quickly ?Ans: It is under dry, warm and windy conditi

ons.

air/water meniscus

graduated capillary tube

reservoir

leafy shoot

tap

Ans: No. It is because it only measures the rate of water uptake by the leafy shoot …

Ans: In addition, it is too small to fit the whole root system and this may affect the rate of water uptake.

Does this apparatus give you an accurate Does this apparatus give you an accurate measurement of the rate of transpiration ?measurement of the rate of transpiration ?

air/water meniscus

graduated capillary tube

reservoir

leafy shoot

tap

Sometimes you may introduce an air Sometimes you may introduce an air bubble into the capillary tube. State the bubble into the capillary tube. State the advantageadvantage of this method. of this method.Ans: Movement of the air bubble is easier to obs

erve than that of air/water meniscus.

air/water meniscus

graduated capillary tube

reservoir

leafy shoot

tap

Sometimes you may introduce an air bubble Sometimes you may introduce an air bubble into the capillary tube. State the into the capillary tube. State the disadvantagedisadvantage of this method.of this method.Ans: Friction between the capillary wall and the bu

bble may affect the movement of bubble.

air/water meniscus

graduated capillary tube

reservoir

leafy shoot

tap

To Measure the rate of To Measure the rate of water uptake and watewater uptake and water loss of a plant using a r loss of a plant using a

weight potometerweight potometer

Change in volume in burette

Change in weight of the whole set-up

= (V2 – V1)cm3

= (W1 – W2)g

= amount of water uptake

= amount of water loss

V2

V1

W1

W224 hours

= (V2 – V1) / 24 cm3/hr

= (W1 – W2) / 24 g/hr

Rate of water uptakeRate of water uptake

Rate of water lossRate of water lossV2

V1

W1

W224 hours

Rate of water lossRate of water loss

>>

Rate of water Rate of water uptakeuptake

Water retained

Photosynthesis / new cells

1cm3 water

=

1g water

in flowering plantsin flowering plantsprovided byprovided by

Transport

consist ofconsist of

carriescarries carriescarries

Concept diagramConcept diagram

vasculartissues

xylem phloem

water organicnutrients

Transport of water and mineral saltsTransport of water and mineral salts

Xylem vessels transport – water– mineral salts

by transpiration pullwater forms a 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

water and minerals absorbed by roots

bud

Transport of organic nutrientsTransport of organic nutrients

Phloem transport - organic nutrients

by translocation

through sieve plates

moving up to growing part

moving down to growing

fruit and root for storage

organic nutrients made by photo-

synthesis