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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

1

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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