14 Ass 7 pt 2 Plant transport

Question 1

As the young leaf matures, the quantity of sugar taken up by the leaf decreases to zero, but the need for water increases.

Suggest and explain why the quantity of sugar taken up by the developing leaf decreases to zero over time, but the need for water increases. 4

Answer 1

The sugar uptake decreases because as the leaf matures from sink to source,

it produces sugar which is transported out of the leaf to the rest of the plant through photosynthesis

the need for water increases due to increased transpiration

and the need to maintain turgidity

Question 2

What types of sugars are transported as part of phloem sap?

Answer 2

Monosaccharides and disaccharides

Question 3

Define the term disaccharide

Answer 3

A sugar made of 2 monosaccharides joined together

Question 4

Define the term polysaccharide and give 3 examples 4

Answer 4

A polymer made of more than 2 sugar monomers and is not a sugar.

starch
glycogen
cellulose

Question 5

Q22 b read context & draw diagram

Answer 5

See memo

Question 6

What causes the mass flow of phloem sap from source to sink?

Answer 6

A pressure gradient in sieve tubes

Question 7

What happens to cause the pressure gradient in plants that causes mass flow?

Answer 7

A decrease in water potential & increase in hydrostatic pressure in phloem sap

Question 8

What causes a decrease in water potential of phloem sap during mass flow?

Answer 8

High sucrose concentration from loading of assimilates into sieve tube elements

Question 9

What causes an increase in hydrostatic pressure of phloem sap during mass flow?

Answer 9

large volume of water moving in and out of phloem tubes by osmosis

Question 10

Define the term transpiration. 3

Answer 10

When water is absorbed through roots

before traveling up the plant

and being released as water vapor through the stomata in the leaves

Question 11

Q 23 b) use table 5.1 to calculate the mean rate of movement of the bubble

Answer 11

(12.5+12+11.5)/3 = 36/3 =12

It’s in 10 minutes and we’re calculating how fast it moves per minute, so 12/10=1.2

1.2 mm min^-1

Question 12

Explain why air movement increases the rate of transpiration

Answer 12

The water potential gradient is steeper from there being less water in the air around the plant

Question 13

Explain how water moves up through a xylem vessel in the stem of the plant 5

Answer 13

Water moving out of the leaf creates tension in the xylem vessel

this allows water to move up, down the water potential gradient

Water molecules are attracted to each other, through hydrogen bonding, forming cohesion

Adhesion is created from water being attracted to polar molecules in cellulose and lignin

This creates a continuous column of water

Question 14

Define adhesion

Answer 14

Water molecules sticking to cellulose molecules in lining of the xylem vessel

Question 15

Q24 b read context and see fig. The general pattern of results in Fig. 4.1 is the same for the three Barlinka
grapevines. Explain why the general pattern of results is the same. 3

Answer 15

During the day, the stomata are open

so the rate of transpiration is higher

The daytime is also warmer

Question 16

Q24 b read context and see fig.With reference to Fig. 4.1, explain the differences in the results between the
three grapevines, 1, 2 and 3. 2

Answer 16

A greater total surface area of the leaf leads to a higher rate of transpiration due to more stomata,

as seen by how grapevine 1 has the greatest surface area and the highest rate of transpiration

Question 17

Q24 b read context and see fig.Suggest an explanation for the decrease in flow rate of xylem sap shown at time P

Answer 17

It could have been cloudy or rainy

Question 18

Outline how you would determine the surface area of one side of a leaf 3

Answer 18

Trace around the leaf over some graph paper

count the number of whole squares

double that number

Question 19

Q19 The diagram shows a model to demonstrate mass flow. In a plant, what is W?

Answer 19

Phloem

Question 20

Q19 The diagram shows a model to demonstrate mass flow. In a plant, what is X?

Answer 20

Xylem

Question 21

Q19 The diagram shows a model to demonstrate mass flow. In a plant, what is Z?

Answer 21

roots

Question 22

Q19 The diagram shows a model to demonstrate mass flow. In a plant, what is Y?

Answer 22

leaves

Question 23

Q19 The diagram shows a model to demonstrate mass flow. In a plant, what is the direction of flow along W?

Answer 23

Y to Z

Question 24

Q20 the diagram shows a xerophytic leaf in different conditions, P and Q. What is the difference btw the cells in layer Y of P and Q? 2

Answer 24

More negative water potential in P than Q

More cells plasmolysed in P

Question 25

Q5 see diagram. What is 1 and how can you identify it?

Answer 25

Xylem, because of pits

Question 26

Q5 see diagram. What is 2 how can you identify it?

Answer 26

Phloem, because it’s small

Question 27

Q5 see diagram. What is 3 how can you identify it?

Answer 27

Amyoplast (stores starch) because it’s big