Topic 9.1 Flashcards
What is the function of the Xylem?
It transports water and dissolved minerals from the roots towards the leaves
What is transpiration?
the loss of water vapor through the leaves of the plant
What causes transpiration?
photosynthesis
Describe the structure of the xylem vessels
They are dead, is hollow on the inside (like a drinking straw). Walls of xylem are reinforced with lignin. They have no end walls (like a drinking straw). perforated plates in cell walls.
Describe the regulation of water loss (how water is lost)
1)Plant begins to lack water and wilt
2) Absisic acid (ABA) hormone is produced
3)Efflux of K+ ions is triggered
4)Water will be lost from guard cells
5) Guard cell will close (because they lost turgor pressure).
What controls the opening of the stomata?
light intensity, CO2 concentration, temperatures, humidity and wind (overall by the rate of photosynthesis).
What is transpiration pull?
when the water is pulled up the xylem, it is caused by high pressure in the roots and low pressure in the leaves.
Describe the process of transpiration pull
1) Light energy hits the leaves
2) water will be heated up by the light energy, thus it will evaporate in the form of water vapor.
3)Water vapor will diffuse out of the leaves through the stomata
4)Negative pressure gradient is created (when there is high pressure in roots and low pressure in leaves)
5)Negative pressure gradient will create tension force in leaves
6) water will be pulled up the xylem.
Explain the absorption of water and minerals from the roots
1) Root cells expel H+ ions (via H+ pumps) to the surrounding soil.
2) H+ ions will displace the positively charged mineral ions.
3) Positive ions will move along the gradient to be reabsorbed by the root cells
4) H+ ions and negatively charged mineral ions will be reabsorbed TOGETHER.
What are the two pathways that water can go through beginning from the roots and to the leaves?
Symplast and Apoplast pathway
Describe the symplastic pathway
water will continuously move through the cytoplasm of the cells
Describe the apoplastic pathway
Water will move through the cell walls only.
Discuss Xerophytes adaptations
1) Less amount of leaves
2) Rolled up leaves
3) Thick, waxy cuticle
4) Stomata in pits
5) Low growth
6) CAM physiology
Discuss Halophytes adaptations
1) Salt excretion
2) Root membranes
3) Abscission
4) Sequestration
5) Flowering schedules
