module 3 - 9.4 translocation

Question 1

how does ATPase create energy?

Answer 1

breaks off the last phosphate to create energy

Question 2

what is translocation?

Answer 2

the movement of nutrients around a plant - transport of sugars and amino acids in the phloem, minerals dissolved and transported in xylem

Question 3

which direction can translocation occur in the phloem?

Answer 3

either direction - it is bidirectional

Question 4

what is the difference between water transport in the xylem and phloem?

Answer 4

phloem - water transport is an active process that requires energy, unlike xylem

Question 5

what are sources?

Answer 5

they provide assimilates to the plant from reactions or storage for transport

Question 6

what are examples of sources?

Answer 6

• green leaves and stems
• storage organs
• food stores in seeds

Question 7

sucrose makes up how much of phloem sap?

Answer 7

20-30%

Question 8

what are sinks?

Answer 8

they use assimilates from the plant in various processes

Question 9

what are examples of sinks?

Answer 9

• active processes in root and stem e.g growing
• meristem cells activity dividing
• developing stores

Question 10

what is phloem loading?

Answer 10

assimilates are moved into phloem by active process

Question 11

what are the 2 route assimilates can be moved into the phloem?

Answer 11

• symplast route (through cytoplasm & plasmodesmata)
• apoplast route (through cell walls)

Question 12

how are H+ ions pumped out during phloem loading?

Answer 12

using ATP against a concentration gradient

Question 13

why do H+ ions return to companion cell with sucrose?

Answer 13

to bring sucrose back through cotransport

Question 14

what do hydrogen ions act as in the apoplast route?

Answer 14

cotransporters and actively move assimilates across the membrane

Question 15

how do sugars move along the phloem at the source?

Answer 15

• sugars actively move into sieve cytoplasm decreasing water potential
• this increases hydrostatic pressure inside phloem, water moves to decrease this pressure

Question 16

how do sugars move along the phloem at the sink?

Answer 16

• assimilates are actively moved/ diffuse out of sieve cells
• this increases water potential so water moves out by osmosis decreasing hydrostatic pressure

Question 17

what would happen if a section/ ring of bark on a tree was taken off around the trunk?

Answer 17

• phloem is in the bark, xylem is in the wood
• area above the cut acts as a sink where sugars collect (bulges)
• no further growth under the cut (needs sugar for growth)