Chapter 9: Transport in Plants

Students should be able to:

1. Relate structure and function of root hairs to their surface area, and to water and ion uptake.

2. State transpiration as the loss of water from aerial parts of a plant, especially through stomata of the leaves.

3. Describe how water loss is related to cell surfaces, air spaces and stomata.

4. Describe effects of temperature, humidity and light intensity on transpiration rate.

5. Describe wilting.6. Investigate the pathway of water using a suitable stain.7. Explain movement of water through the stem in terms of

transpirational pull.8. Identify the position of the xylem and phloem as seen in the TS of a

dicotyledonous stem and leaves.9. State the function of the xylem and phloem.

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 saltsRoot hair cell is living Provide energy for active transport by

respiration1. Cell sap conc. > Soil

solution conc.2. Cell sap is prevented from

leaking out of root hair cell

Water enters by osmosis

9.2 Transport & Vascular Tissue

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9.2.1 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, hollow tube from root to leaf

Hollow space (lumen) is continuous

Vessel is a dead structure

Wall is strengthened by lignin

Does not hinder passage of water

Provide mechanical support to the plant

9.3 Investigating Pathway of Water

9.4.1 Internal structure of a dicotyledonous stem

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Make up the phloem

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, provides energy required for active transport

9.4.2 Internal structure of a dicotyledonous root

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 H 2O 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

Water Vapour Loss Water Vapour

Loss

Thin film of moisture over surface of intercellular air spaces

Forming

Water evaporates out of intercellular air spaces

Water vapour goes out through stomata

Phloem

Cambium

Xylem

Xylem + Phloem arranged in a ring

Cuticle prevents evaporation of water

Store food substances

Xylem

Phloem

Xylem + Phloem lie on different radii, alternating with each other

Epidermis is called a piliferous layer no cuticle (Why?) (Hint: What is the role of the roots in a plant?)

9.5.2 Factors affecting transpiration rate

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Suction force from transpiration pulls water & m.s from roots to leaves

As water evaporates cools the plant

Impt of transpiration

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)

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Transpiration Rate

Water Evaporation Rate

HumidityTemp. Of air Light intensity

Wind condition

Humidity transpiration rate Temp

transpiration rate

L.I. size of stomata

Transpiration rateWHY??

Windy external air

Blow away water vapour

Humidity

Transpiration rate

Note: Humidity amt of water vapour

Turgor pressure Support of Leaf Strong sunlight

Transpiration rate

Cells lose water

Turgor pressure

Cells become flaccidStomata close

9.7 Transpirational Pull

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