plant sugar transport

Question 1

what is the pressure flow hypothesis?

Answer 1

1) source (leaf) cells move sugar into companion cells, which is moved into sieve tube via active transport (low –> high)
2) water moves from xylem to sieve via osmosis, turgor pressure increases
3) overall pressure increases, moving sap down gradient towards sinks (roots)

Question 2

what phenotypic change is caused by a nitrogen deficiency?

Answer 2

yellow leaves

Question 3

what phenotypic change is caused by a phosphorous deficiency?

Answer 3

brown leaves

Question 4

what are the steps for ion uptake?

Answer 4

1) proton pumps establish electrochemical gradient with protons
2) cations cross membrane through gradient in ion channels
3) anions enter membrane using protons and cotransporters, H ions returned inside cell

Question 5

what is passive ion exclusion?

Answer 5

limited/lack of transporters for certain ions, or using casparian strip to block ions entering apoplastically

Question 6

what is active ion exclusion?

Answer 6

metallothioneins and phytochelatins bind to metal ions, tonoplasts store unwanted ions