13 Ass 7 pt 1 Plant Transport

Question 1

what DO phloem sieve tube elements have? 9

Answer 1

Cellulose cell walls,
cell membrane
cytoplasm
endoplasmic reticulum
Lots of mitochondria
end walls
sieve plate
companion cells
plasmodesmata

Question 2

what DON’T phloem sieve tube elements have? 5

Answer 2

Nucleus
ribosomes
lignin
pits
spiral structures

Question 3

What DO xylem vessel elements have? 3

Answer 3

Lignin cell walls
pits
spiral structures

Question 4

what DON’T xylem vessel elements have? 5

Answer 4

nucleus
sieve plates
mitochondria
cytoplasm
end walls

Question 5

Why do xylem vessel elements have pits btw vessels?

Answer 5

To allow water to pass from vessel to vessel

Question 6

Why are xylem vessel elements thickened with lignin?

Answer 6

To stop them collapsing when water column is under tension

Question 7

Why do xylem vessel elements form a continuous hollow tube through plant?

Answer 7

It provides little resistance to water movement

Question 8

What is the ratio of cell wall width to whole cell width in a xylem vessel element?

Answer 8

around 1:10, cell wall is very thick

Question 9

Under a microscope, what structures would likely be observed in a xylem vessel element?

Answer 9

None

Question 10

What’s the ratio of cell wall width to whole cell width in a Phloem sieve tube element?

Answer 10

around 1:20, cell wall thinner than xylem

Question 11

Under a microscope, what structures would likely be observed in phloem sieve tube elements?

Answer 11

regular pattern of circles in some cells

Question 12

Under a microscope, what would likely be observed in companion cells?

Answer 12

granular appearance

Question 13

What DO companion cells have? 4

Answer 13

Lots of mitochondria
lots of ribosomes
highly metabolically active
lots of plasmodesmata

Question 14

What contributes to upward movement of water in a xylem vessel of a plant? 6

Answer 14

Cohesion of water molecules
- through hydrogen bonding

Adhesion of water molecules to the cellulose walls of xylem vessels
- by hydrogen bonding

removal of water from xylem vessels in a leaf
- reduces hydrostatic pressure in xylem

Question 15

What term is used to describe the attraction of water molecules to each other?

Answer 15

cohesion

Question 16

What is the sequence of parts of the root that the water must travel through to move across the root? 3

Answer 16

Cell walls of cortex cells

endodermal cells

Xylem vessels

Question 17

Why is transpiration an inevitable consequence of gas exchange in plants?

Answer 17

Stomata must be open

Question 18

What is an example of a mass flow system in a plant?

Answer 18

The movement of sap through the phloem sieve tubes in the stem

Question 19

Q13 look at graph and read context. What can be concluded from the graph? 3

Answer 19

The rate of water absorption and the rate of water loss peak at 16:00

The rate of water loss is greater than the rate of absorption for 12 hours

The rate of water absorption is greater than the rate of water loss at night

Question 20

The diameter of a tree trunk usually decreases slightly during the day. what changes in environmental factors during the day could cause the diameter to decrease more? 3

Answer 20

Increased light intensity

Increased wind speed

increased temperature

Question 21

Q15 A student wanted to find the rate of transpiration using a potometer as shown. The student was told to work out the value for transpiration using units mm^3, m^-2, and hour^-1. Which measurements would the student need to take? 4

Answer 21

distance air bubble moves,
radius of capillary tubing,
time
surface area of the leaves

Question 22

SUCROSE IS LOADED into phloem sieve tubes from companion cells. What is the correct order of statements that explains this mechanism? 4

Answer 22

Hydrogen ions are pumped out of companion cells by active transport

Hydrogen ions diffuse into companion cells through co-transporter proteins

sucrose is co-transported along with hydrogen ions

sucrose diffuses into phloem sieve tubes via plasmodesmata

Question 23

Which sequence of events could lead to MASS FLOW in a phloem sieve tube? 6

Answer 23

Protons (H+) are actively pumped out of a companion cell

Protons (H+) and sucrose molecules move into a companion cell through a co-transporter protein

sucrose moves into a sieve tube element

The water potential of sieve tube element decreases

Water moves down water potential gradient by osmosis

A very high hydrostatic pressure is produced

Question 24

What are proton pumps (H+ pumps) and co-transporters are used for?

Answer 24

Used in plants plants when loading sucrose into a phloem sieve tube element at a source.

Question 25

How do proton pumps work?

Answer 25

They pump protons out of a companion cell into its cell wall

Question 26

How do co-transporters work?

Answer 26

The high concentration of protons outside a companion cell drives the transport of sucrose into the cell