mass transport in plants- translocation

Question 1

what is translocation

Answer 1

the mass flow of solutes (e.g. sucrose) in the phloem, down a pressure gradient (from source to sink)

Question 2

describe events at the SOURCE in translocation

Answer 2

• companion cells actively transport solutes (e.g. sucrose) into the adjacent phloem
• lowers water potential in phloem sieve cells
• water diffuses in by osmosis (from xylem)
• increases hydrostatic (turgor) pressure

Question 3

describe events at the SINK in translocation

Answer 3

• solutes (e.g. sucrose) actively transported from phloem to sink
• raises water potential in phloem sieve cells
• water diffuses out by osmosis (into xylem)
• decreases hydrostatic (turgor) pressure

Question 4

define the source

Answer 4

tissue that is producing/releasing an excess of organic molecules (e.g. photosynthesising leaves)

Question 5

define the sink

Answer 5

tissue that is using/storing the products of photosynthesis (organic molecules) (e.g. growing root tips, growing shoot tips)