Water transport

Question 1

What are the 4 kingdoms of vascular plants?

Answer 1

Lycophytes
Pterophytes
Gymnosperms
Angiosperms

Question 2

What are the two types of xylem?

What are the similarities and differences between them?

Answer 2

Tracheids
Tracheary

Both types have pits in their cell walls and are dead when in use for transport.
Tracheary vessel elements are stacked and have perforations at the top and bottom.

Question 3

What kingdom of vascular plants do tracheary vessel elements exist in?

Answer 3

Angiosperms

Question 4

What are the two types of phloem conducting cells?

What are the similarities and differences between them?

Answer 4

Sieve cells
Sieve tube members

Both types are live cells with dense areas of channels between cells (sieve areas) and have a thick secondary cell wall.
Sieve tube members are stacked and have a sieve plate on each extremity.

Question 5

What are the four factors that can affect water potential?

Answer 5

• osmotic potential (decreases with solute concentration)
• pressure potential (often from the cell wall)
• matric potential (temperature increases water potential)
• gravimetric potential

Question 6

Does water move from a high to low or a low to high water potential?

Answer 6

Low to high.

Question 7

What is osmosis?

Answer 7

Diffusion of water across a selectively permeable membrane.

Question 8

What is turgor?

Answer 8

Water inside the cell exerts turgor pressure on the cell wall, which in return exterts wall pressure on the water.

Question 9

What moves in and out of the stomata?

Answer 9

IN
Carbon dioxide

OUT
Water
Oxygen

Question 10

How do the guard cells open and close?

Answer 10

Increase in turgor makes them open.

influx of ions -> water influx -> turgor increases

Question 11

What are aquaporins?

Answer 11

Protien channels forming inside the plasma membrane through which water can flow. They can be shut under certain conditions.

Question 12

What drives water movement in plants?

Answer 12

• transpiration from leaves creates a higher water potential in the leaf
• water moves up the xylem in a narrow, unbroken column with help from adhesion and cohesion tension

Question 13

What is cavitation?

Answer 13

The result of a breakage of the water column in the xylem caused by a bubble blocking the movement in the vessle.

• may occur in droughts or frozen soil

Question 14

How are plants adapted to reduce cavitation?

Answer 14

Multiple tracheids or tracheary vessels so that if one water column there are others that still work.

Question 15

What is root pressure?

Answer 15

There is a higher concentration of ions in the root xylem than in the soil solution creates a difference in water potential driving root pressure (osmotic push from the roots).

Question 16

What is guttation?

Answer 16

An effect caused by root pressure where a small bead of water forms at the very tip of a leaf. Root pressure has driven the water up the water column even when there is no transpiration.

Question 17

How does movement in the phloem work?

Answer 17

Phloem conduction is driven by differences in sugar concentration between source and sink:

• Sugar is loaded into phloem sections near photosynthetic tissue, attracting water by osmosis, increasing turgor pressure.
• In phloem sections near sugar sinks, turgor pressure is reduced.
• Because of mass flow, water carries solutes along the sieve tube.