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Chapter 9: Transport in Plants
9.1 A Recap on Structure and Function of Root Hair Cells
Structure AdaptationLong and narrow SA: vol. Ratio enhance rate of absorption
of H2O and mineral salts
Root hair cell is living Provide energy for active transport byrespiration
1. Cell sap conc. > Soilsolution conc.
2. Cell sap is prevented fromleaking out of root hair
cell
Water enters by osmosis
9.2 Transport & Vascular Tissue9.2.1 Xylem
9.2.2 Phloem
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Functions
Conduct water &
mineral salts from
roots stem
leaves
Provide
mechanical
support for the
plant
Structure
Long, hollowtube from root
to leaf
Hollow space
(lumen) iscontinuous
Vessel is a deadstructure
Wall isstrengthened by
lignin
Does not hinderpassage of water
Providemechanical
support to the
plant
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9.4.1 Internal structure of a dicotyledonous stem
9.4.2 Internal structure of a dicotyledonous root
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Make u the hloem
Function: Conduct manufactured food (sucrose & amino acids) from leaves to
other parts of the plant
Cross-walls separating
sieve tube cells
Thin layer of
cytoplasm
Food moves by diffusion &
active transport
Living cells, providesenergy required for active
transport
Phloem
Cambium
X lem
Xylem + Phloemarranged in a ring
Cuticle prevents
evaporation of
water
Store food substances
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9.5 Transpiration
Definition: The loss of water vapour from the aerial parts of the plant,
especially through stomata of the leaves
9. 5.1 Loss of H2O by plants
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Water vapour loss from
Evaporate from
surface of epidermal
cell
Water moves out of
mesophyll cells
Cuticular
transpiration
Stomata Open Stomata
Closed
WaterVapour Loss
WaterVapour Lo
Thin film of moisture
over surface of
intercellular air spaces
Forming
Water evaporates out of
intercellular air spaces
Water vapour goes
out through stomata
X lem
Phloem
Xylem + Phloem lie on differentradii, alternating with each other
Epidermis is called a piliferouslayer no cuticle (Why?) (Hint:
What is the role of the roots in a
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9.5.2 Factors affecting transpiration rate
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Transpiration Rate
Water Evaporation Rate
HumidityTemp. Of air Light intensity
Wind condition
Humiditytranspiration rate Temp
transpiration rate
L.I. size ofstomata
Transpiration rateWHY??
Windy external air
Blow away water
vapour
Humidity
Transpiration rate
Note:
Humidityamt of watervapour
Suction force from transpirationpulls water & m.s from roots to
leaves
As water evaporates cools thelant
Im t of trans iration
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9.6 Wilting
Advantages of wilting Cells lose water
Disadvantages of wilting
When stomata closes amt of CO2 entering leaf
photosynthetic rate (since photosynthesis uses CO2)
9.7 Transpirational Pull
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Turgor pressure Support of Leaf Strong sunlight
Transpiration rate
Cells lose water
Turgor pressure
Cells become flaccidStomata close
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