1. 9.2 - Transport in Angiospermophytes

2. Transport in Angiospermophytes

3. Minerals in the Soil
Minerals must be able to move through the soil to the roots of plants to be absorbed - how do they do this?
Diffusion -
Fungal hyphae -
Dissolved in soil water -
9.2.2

4. Mineral Uptake Minerals are absorbed by the plant via active transport
Minerals include potassium, phosphate, nitrates and other ions
The concentration of ions is higher inside the root cell than in the surrounding soil
Move against the concentration gradient
Allows for selective absorption of minerals by plants
Cortex cells absorb mineral ions that are dissolved in water
From cortex, minerals dissolved in water travel through the endodermis and into the vascular cylinder.
9.2.3

5. Mineral Uptake
9.2.3

6. Mineral Uptake
9.2.3

7. Vascular Tissue - Xylem
Xylem – water and mineral conducting tissue
At maturity, cells are dead and lack plasma membranes – so water flows through freely
End walls break down forming long tubes
Pores in side walls allow water movement between adjacent cells
9.2.6

8. Vascular Tissue - Xylem
Composed of tracheids and/or vessel elements
Tracheids:
Narrow cells arranged in columns
Overlapping ends help with support and water movement
Vessel Elements:
Cell wall arranged in a helical pattern that enable walls to withstand pressure and stretch as other living cells grow
Wide diameter allows for efficient water transport
Only found in angiosperms
9.2.6

9. Vascular Tissue - Xylem
9.2.6

10. Vascular Tissue - Xylem
9.2.6

11. Transpiration
Transpiration - the loss of water vapor from the leaves and stems through evaporation
Plants are adapted to limit water loss – how?
9.2.5
9.2.6

12. Transpiration

13. Transpiration Stream
Transpiration stream - transpiration creates a flow of water from the roots, through the stems, to the leaves
Movement of water through plants depends on the cohesion and adhesion of water molecules - what are these properties?
Water forms a column due to hydrogen bonding
9.2.6

14. Transpiration Stream Steps in water movement:
Water evaporates from spongy mesophyll in leaf tissue (transpiration)
Water is replaced with water from xylem tissue in leaf veins
Water moves into leaf tissue via capillary action
When water is pulled out of xylem, suction develops, and more water is pulled up from roots and stem – transpiration pull
Like using a straw to suck up liquid
9.2.6

15. Transpiration Stream
9.2.6

16. Regulation of Transpiration
Water evaporates out of the leaf tissue through the stomata (transpiration)
Guard cells control transpiration by opening and closing the stomata
Generally, guard cells open stomata during the day and close them at night - why?
9.2.7

17. Regulation of Transpiration
Changes in turgor pressure in the guard cells open and close the stomata:
Guard cells actively uptake potassium ions (K+) and increase solute concentration
Water enters the guard cells by osmosis to balance solute concentration and cells become turgid.
Turgid guard cell = open stomata
Reverse process makes guard cells flaccid and closes stomata
Flaccid guard cell = closed stomata
9.2.7

18. Regulation of Transpiration
9.2.7

19. Regulation of Transpiration
9.2.7

20. Regulation of Transpiration
Environmental factors and stressors can also affect transpiration and opening and closing of the stomata:
When plants are water deficient, cells may lose turgor and stomata close - why important?
Abscisic acid, a plant hormone, signals stomata to close during water deficiencies.
9.2.8

21. Factors Affecting Transpiration
Light – guard cells close in darkness, open in light – why?
Increased transpiration during day
Temperature – higher temperatures increase transpiration
Also decrease outside humidity – thus increase diffusion out water out of leaf
9.2.9

22. Factors Affecting Transpiration
Humidity – lower humidity increases transpiration – why?
Wind – air movement moves air saturated with water vapor away from stomata – thereby increasing transpiration
9.2.9

23. Xerophytes Plants adapted to grow in very dry environments
Have evolved different adaptations to help reduce transpiration - why?
9.2.10

24. Xerophytes Adaptations of Xerophytes: Spines instead of leaves – why?
Thick stems with water storage tissue
Thick, waxy cuticle
Vertical stems instead of lateral reaching branches – why?
Wide-spreading network of shallow roots – why?
9.2.10

25. Vascular Tissue - Phloem
Phloem – sugar and amino acid conducting tissue
Formed from long chains of sieve-tube members
Alive a maturity (however they lack nuclei and ribosomes)
End walls (sieve plates) have pores that allow for flow of sugar between cells
Each sieve tube cell has an adjacent companion cell that helps serve sieve tube member
9.2.11

26. Vascular Tissue - Phloem
9.2.11

27. Translocation
Translocation – movement of substances from one area in a plant to another
Moves sugars and amino acids from source areas (photosynthetic tissue and storage organs) to sinks (fruits, seeds, and roots)
Active process that occurs in phloem
9.2.11

28. Translocation How Translocation Works:
Plasma membranes in sieve tube members pump organic compounds into cell via active transport
Creates high solute concentration inside sieve tube member
Therefore, water diffuses into sieve tube via osmosis - forms sap (sugars dissolved in water)
Creates pressure inside sieve tube and pushes sap throughout plant
9.2.11

29. Translocation
9.2.11

30. Translocation
Sugar loading in sieve tube raises solute concentration and draws in water
Water influx increases pressure forcing flow of sap
Sugar unloading lowers solute concentration, water effluxes and pressure decreases
Water pulled back up via transpiration stream
9.2.11

31. Translocation
9.2.11