Chapter 9 Transport in Plants - Lecture Notes
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Transcript of Chapter 9 Transport in Plants - Lecture Notes
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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