translocation

Question 1

what is translocation in the phloem

Answer 1

movement of assimilates e.g. Sucrose and amino acids from sources were, they are produced two sinks, where assimilates are removed from the sieve, tubes and used

Question 2

What are examples of sources and sinks?

Answer 2

sources :
leaves
Storage organs, e.g. tubers
(produce more sugar than they need)

sinks:
Developing fruits
Roots
Young shoots
Developing seeds
(don’t produce enough sugar for their needs)

Question 3

What are the two features of translocation?

Answer 3

Active loading

Mass flow of sap in the phloem

Question 4

Explain, active loading

Answer 4

1) hydrogen ions pumped out of companion cell by active transport using ATP
2) this creates a hydrogen ion concentration gradient
3) hydrogen ions, return to companion cell with sucrose via co-transport, protein, bye, facilitated diffusion
Also called secondary active transport

Question 5

Explain mass flow of sap in the phloem

Answer 5

1) sucrose moves out of the companion cell into sieve tube element by diffusion and reduces the water potential
2) water follows by osmosis from xylem and increases hydrostatic pressure in s sieve tube element
3) water moves down, sieve tube from high hydrostatic pressure, too low, hydrostatic pressure at sink
4) sucrose is removed from sieve tube to surrounding cells and increases the water potential in sieve tube
5) water moves out of a sieve tube and reduces the hydro static pressure