Transport in plants Flashcards
(10 cards)
Why do multicellular organisms need transport systems?
(3)
To meet high metabolic demand
Ensure nutrients reach all tissues
Allow diffusion across large distances
What are the 3 factors that affect the rate of transpiration?
Light (as it opens the stomata)
Temp (kinetic energy and evap)
Wind/Humidity affect the water potential outside the leaf
What are the 2 pathways in which water is reabsorbed?
Symplast pathway
Apoplast pathway
What is the Symplast pathway?
This is where water travels through cytoplasm’s connected via plasmodesmata until the xylem
What is the Apoplast pathway?
This is where water travels through cell walls until the impermeable casperian strip so it shifts to the Symplast pathway
How does water travel up the xylem?
Cohesion and H - bonds
What are Xerophytes and 4 adaptations of it?
Plants with limited water
-Closed stomata
-Thick waxy cuticle (big diffusion distance so water don’t leave)
-Hairs (traps water)
-Stomata in pits (less evap)
What is translocation (Def)?
The moment of water dissolved substances from source to sink
Please explain translocation in the phloem from source to sink
(6)
1)Sucrose moves from source cell to companion cell into the sieve tube element
2)This causes the water potential in the sieve tube element to decease(water pot gradient)
3)Water from the xylem moves in via osmosis
4)This causes hydrostatic pressure to increase in the sieve tube element
5)Cuz of this there is now a hydrostatic pressure gradient from source to sink which the sucrose moves down
6)Sucrose moves in from sieve tube element to companion cell to sink cell
What are the 3 pieces of evidence that determine whether a piece of evidence is in support of the mass flow hypothesis
- H2O moves in and out of the phloem via osmosis
- Pressure moves the sucrose solution
-Its an active process that uses ATP (companion cells have mitochondria)
