1. Plant Transport
NT: 190 – 199
Bill Indge:

2. Structure of the Root root hairs zone of differentiation (maturation)
lengthening cells in this region pushes the root tip through the soil
root meristem
region of cell division (mitosis)
root cap

3. Root structure

4. Structure of a Plant Root

5. The passage of water through a plant (missing answers HB p11):
Root
Xylem
Stem
Leaves
Stomata pores
Transpiration

7. See next slide to help you add water potential values to the diagram

9. What is the function of root hairs?
To absorb water and mineral ions.

10. How are root hairs adapted for their function?
Have a large Surface Area to Volume ratio, so more water and mineral ions can be absorbed at the same time.
Root hairs have a thinner cellulose cell wall which reduces the diffusion pathway.
Now do the following annotations 1-7 for the diag at top of p12 handbook :

12. Entry of water into the roots, up a plant and out of the leaves.
1. Water enters root hairs by osmosis as the water potential of the cells in the root hairs is _______ negative than that of the soil.
more

13. Structure of a Root 2 possible pathways through which water may pass
Showing one of the routes by which water and mineral salts may be drawn from the soil into the vascular tissue.
root hair
air space
soil particle
endodermis
xylem vessel
cortex (parenchyma)
2 possible pathways through which water may pass
Apoplast pathway through all cell walls
Symplast pathway through cytoplasm and plasodesmata

14. plasmodesmata
There are 2 possible pathways through which water may pass:
(A) Symplast pathway: Water passes through cytoplasm and plasodesmata
(B) Apoplast pathway: Water passes through the cellulose cell walls

15. Water moves through the cytoplasm by ________
2. The passage of water through the cytoplasm is called the symplast pathway.
As water enters the cell it _______ the water potential of that cell so it becomes _____ negative than that of the next cell, so water passes from cell to cell down the water potential gradient into the root.
Water moves through the cytoplasm by ________
raises
less
osmosis

16. APOPLAST PATHWAY
SYMPLAST PATHWAY

17. 3. The passage of water through the cellulose cell walls of adjacent cells is called the apoplast pathway.
This occurs due to cohesion (attraction) forces between water molecules due to hydrogen bonding.

18. How does the water then enter the xylem vessels?
At the endodermis the casparian strip, a layer made of impermeable suberin molecules halts the apoplast pathway forcing water into the cytoplasm and thus the symplast route.
Mineral salts are actively transported by the Endodermal cells into the xylem vessels. This then encourages the entry of water into the xylem by osmosis.

20. 4. Cohesion maintains a ‘chain’ of water molecules that moves up the xylem vessels of the root and stem (due to hydrogen bonding).
5. Water moves across leaf cells by osmosis and cohesion.
6. Heat energy causes water to evaporate from leaf cells into the air spaces of the leaf
7. Water moves out of the leaf by diffusion through the stomata. (transpiration)

21. See good transpiration animation link

23. Biology Test First lesson back after half term break
The Blood Circulatory System (mass flow)
Blood Vessels
Blood, Plasma, Tissue Fluid & Lymph.
Plant Transport of Water
Leaf Structure and Xerophytic Adaptations.
Check HW answers from p189 on p252 and check answers from p195 using pp

24. Capillary Action
Some water can move up a short distance of a very narrow tube by capillary action. To explain this, learn notes about hydrogen bonding and cohesion tension forces, and also the forces of adhesion (ref HB p13)

25. Structure of a Plant Root
Xylem Vessels

26. Now complete the 2 paragraphs in your handbook p13 using the words below:
Root pressure:
Symplast, more, actively transported endodermal, xylem, osmosis, Casparian
Cohesion – tension :
Osmosis, evaporated, strong cohesion forces, more negative, inwards, hydrogen bonds, narrower, lignin, impermeable, mesophyll, more, strong

27. Missing words from middle of HB p13 in the correct order:
Casparian
Symplast
Actively transported
Endodermal
Xylem
More
Osmosis

28. Missing words from the bottom of HB p13 in the correct order:
Evaporated
More
Osmosis
More negative
Strong cohesion forces
Lignin
Strong and impermeable
Inwards
Narrower

29. Loss of water from the leaf.
What is transpiration?
Loss of water vapour by diffusion/evaporation from the open stomata pores of leaves.
What is the Transpiration stream ?
The movement of water going into, up and through a whole plant, including the loss of water vapour by evaporation from the leaves of a plant.

30. Stomata
Open
In the daylight-
There is the highest rate of transpiration
The guard cells swell up and bend, opening the stomata pore and water evaporates out, down the water potential gradient.
Do the tasks from the middle of HB p14, using AS Textbook p195 to help you.

31. Now complete the Application exercise on page 195 of your text book.
END.