Mass Transport In Plants Flashcards
(31 cards)
What blocks the apoplast pathway in the root endodermis?
Casparian strip
Which pathway does water take to enter the xylem from the endodermis?
Symplast pathway only
How are ions moved into the xylem by the endodermis?
Active transport
What happens to water potential in the xylem when ions enter?
Water potential lowers in the xylem
How does water enter the xylem from the endodermis?
By osmosis, down a water potential gradient
What causes water to move from the xylem to the leaves?
Evaporation/transpiration from leaves
What forces in the xylem are created by transpiration?
Cohesion, tension, and hydrogen bonding between water molecules; negative pressure
How do water molecules interact with the xylem walls?
Adhesion/bind to xylem walls
What structure does water form as it moves up the xylem?
Continuous column of water
What causes root pressure?
Active transport of ions/salts into the xylem by endodermis
How does ion movement affect water potential in the xylem?
Lowers water potential in xylem
How does water enter the xylem due to root pressure?
By osmosis
Name one factor that affects transpiration.
Light intensity / temperature / air movement / humidity
What should you do to prevent air entering the potometer joints?
Seal joints to ensure airtight and watertight conditions
How should the shoot be cut to ensure reliable water uptake measurement?
Cut shoot under water and at a slant
What should you do to the leaves before placing the shoot in the apparatus?
Dry off leaves
How do you avoid air bubbles when setting up a potometer?
Insert shoot under water and ensure no air bubbles are present
What must you do with the tap and air bubble before starting measurements?
Shut tap and move bubble to the start position
Where are sugars actively transported into the phloem?
In the source (leaf)
What cells actively transport sugars into the phloem?
Companion cells
What effect does sugar loading have on water potential in sieve tubes?
Lowers water potential in sieve tube
How does water enter the sieve tubes after sugar loading?
By osmosis
What does the increase in hydrostatic pressure in sieve tubes cause?
Mass flow/movement towards sink/root
How are sugars used at the sink?
Used or converted for respiration or storage
