high hydrostatic pressure - Transport in Flowering Plants

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Topic Overview
Transport in Plant Nutrition
6.1 Stem & Root
Structure & Function
6.1.1 Vascular Bundle
Structure &
Function
6.1.2 Stem Internal
Structure
6.1.3 Root Internal
Structure
6.1.4 Leaf Internal
Structure in
Relation to
Vascular Bundle
Arrangements
6.2 Transport of Water
& Minerals
6.3 Transports
in Phloem
6.2.1 Water Potential
6.2.2 Overview of Water Movement
6.2.3 Water Movement in Roots
6.2.4 Mechanism of Water & Mineral
Transport in Stems
i) Root Pressure
ii) Capillary Action
iii) Transpiration & Transpiration
Pull
6.2.5 Water Movement in Leaves
6.2.6 Factors Influencing Water
Movement and Water Loss
6.2.7 Wilting
6.4 Water Relations &
Leaf Adaptation
6.3.1 Pressure Flow
Hypothesis
6.3.2 Evidence for
Sucrose
Translocation
6.4.1 Hydrophytic
Leaves
6.4.2 Xerophytic
Leaves
Phloem Transport
Xylem is UNIDIRECTIONAL.
Phloem is BIDIRECTIONAL.
Do you think transpiration pull is a
model that can sufficiently explain
phloem transport?
What do you think is necessary in
order for phloem sap to move?
Phloem Transport
Yes! You need a Driving Force!
In order for a Driving Force to be
established…
You need to have some form of
GRADIENT.
Pressure Flow Hypothesis
Difference in Hydrostatic Pressure
1) SUGAR SOURCE:
Parts of plant where excess sugar
being released or produced.
2) SUGAR SINKS:
Parts of plant where sugar is
consumed or stored.
Sugar moves to SOURCE to SINK.
Phloem Transport
Phloem Loading
1. Sugar is first “loaded” from
SUGAR SOURCE into Phloem
by the Companion Cell.
2. Requires Energy.
3. Phloem  Water Potential
becomes MORE NEGATIVE
4. Water from Xylem enters
Phloem by Osmosis.
5. High Hydrostatic Pressure in
Phloem
HIGH
HYDROSTATIC
PRESSURE
Phloem Transport
Phloem Unloading
1. Sugar is unloaded from
Phloem into storage tissues
2. Requires Energy
3. Phloem  Water Potential
becomes LESS NEGATIVE
4. Water from Phloem returns to
Xylem by Osmosis.
5. Low Hydrostatic Pressure in
Phloem
LOW
HYDROSTATIC
PRESSURE
Pressure Flow Hypothesis
Difference in Hydrostatic Pressure
1.
Phloem Loading in Sugar Sources:
High Hydrostatic Pressure
2.
Phloem Unloading in Sugar Sinks:
Low Hydrostatic Pressure
http://highered.mcgrawhill.com/sites/9834092339/student_view0/
chapter38/animation__phloem_loading.html
Evidence for Phloem Transport
1. Use of Aphids
2. Use of Radioactive Carbon Isotopes
3. Bark-Ringing Experiments
Evidence for Phloem Transport
1. Use of Aphids
Aphids extract phloem sap by inserting their
proboscis into the phloem.
1. Anaesthetize aphids with CO2 while they are
feeding.
2. Sever aphid body with laser.
3. Phloem sap flows out of severed
proboscis by hydrostatic pressure.
4. Analyse phloem sap.. Voila! Sugars
found!
Evidence for Phloem Transport
2. Use of Radioactive Carbon Isotopes
1. Carbon-14, radioactive
isotope of carbon.
2. Incorporated into CO2 .
3. Administered to plant.
4. Section plant and put on
photographic plate.
Evidence for Phloem Transport
3. Bark-Ringing Experiments
Recall: Where is the position
of the Phloem relative to the
Xylem in a Dicot Stem?
Pith
Epidermis
Cortex
Vascular
Bundle
Topic Overview
Transport in Plant Nutrition
6.1 Stem & Root
Structure & Function
6.1.1 Vascular Bundle
Structure &
Function
6.1.2 Stem Internal
Structure
6.1.3 Root Internal
Structure
6.1.4 Leaf Internal
Structure in
Relation to
Vascular Bundle
Arrangements
6.2 Transport of Water
& Minerals
6.3 Transports
in Phloem
6.2.1 Water Potential
6.2.2 Overview of Water Movement
6.2.3 Water Movement in Roots
6.2.4 Mechanism of Water & Mineral
Transport in Stems
i) Root Pressure
ii) Capillary Action
iii) Transpiration & Transpiration
Pull
6.2.5 Water Movement in Leaves
6.2.6 Factors Influencing Water
Movement and Water Loss
6.2.7 Wilting
6.4 Water Relations &
Leaf Adaptation
6.3.1 Pressure Flow
Hypothesis
6.3.2 Evidence for
Sucrose
Translocation
6.4.1 Hydrophytic
Leaves
6.4.2 Xerophytic
Leaves
Leaf Adaptations to Harsh Conditions
“Normal” plants are known as Mesophytes.
1. Xerophytic adaptation
2. Hydrophytic adaptation
3. Halophytic adaptation
Leaf Adaptations to Harsh Conditions
1. Xerophytic adaptation
1. Limit Water Loss
2. Water Storage
3. Water Acquisition
Leaf Adaptations to Harsh Conditions
2. Hydrophytic adaptation
1. Gaseous Exchange
2. Floatation

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