Evidence supporting mass flow

Question 1

When the phloem sieve tube is punctured……………….. oozes out

and what does this suggest

Answer 1

phloem sap

This suggests that it is under pressure

Question 2

Phloem sap taken from near a source has a ………. than sap taken from near a sink

what does this suggest

Answer 2

higher sucrose concentration

This suggests that different water potentials would result in osmosis into/out of the sieve tubes at those two locations

Question 3

When a plant virus is applied to leaves that are well-lit the virus can be

what doe sthis suggest

Answer 3

observed moving down the phloem towards the roots

This demonstrates the bulk flow of substances in one direction

Question 4

When the virus is applied in the dark it is not………………..

what does this suggest

Answer 4

transported

This suggests that for translocation to occur photosynthesis and the production of sucrose is required in the source tissue