Transport In Plants

Question 1

How many transport systems does a plant have

Answer 1

They have 2 systems, the xylem and phloem

Question 2

What does the xylem tissue do

Answer 2

Transports water and minerals ions from the roots to the leaves, stem and flowers

Question 3

What does the phloem tubes do

Answer 3

The phloem tubes transport dissolved sugars and other soluble food molecules from the leaves to all of the other areas of the plant

The sugars are made during photosynthesis which is why they come from the leaves

Question 4

What are meristems

Answer 4

The place where plant stem cells are produced

Question 5

What is the process of moving sugars around the plant through the phloem called

Answer 5

Translocation

Question 6

What is the structure of the xylem

Answer 6

• the xylem vessels are made form dead xylem cells
• they form tubes which run through the plant stems
• there are no cell walls at the end of these cells
• strengthened with a substance called lignin

Question 7

What is the structure of the phloem

Answer 7

• Phloem vessels are made of living cells
• the walls of the cells do not completely break down
• sieve plates are formed (they are small holes in the end wall which allow the dissolved sugars to pass through)
• the connection of phloem stems forms a tube which allows dissolved sugars to be transported

Question 8

How do the vascular bundles provide support in the leaf

Answer 8

• ## in the leaf they form a network that supports the softer leaf tissue

Question 9

How does the evaporation of water from the leaves work

Answer 9

The water molecules are taken up from the roots to the leaves by the xylem cells.

• as the water molecules travel up into the leaves, the guard cells become turgid, and the stomata open
• the water flows out of the leaf through the stomata, due to the concentration gradient
• inside the leaf, there is a high concentration of water, but outside in the air, there is a low concentration
• while the stomata are open, CO2 is then able to flow into the leaf, which is used to fuel photosynthesis

Question 10

Transpiration stream definition

Answer 10

The chain of water molecules that travel up the Xylem cells

Question 11

Transpiration meaning

Answer 11

The evaporation of water from the leaves

Question 12

What factors effect the rate of transpiration

Answer 12

• humidity
• light intensity
• temperature
• air flow

Question 13

How does light intensity effect rate of transpiration

Answer 13

• Brighter light means that more photosynthesis will occur, meaning that more carbon is needed.
• This mesns the stomata will be opened more to allow carbon to enter
• More water will be lost from leaf when stomata are open meaning higher rate of transpiration

Question 14

How does temperature affect the of transpiration

Answer 14

The warmer it is, the higher the rate of transpiration

• the water particles will have ore energy, so they will be more likely to evaporate and diffuse out of the stomata
• low temperature means evaporation takes place slower

Question 15

How does wind speed effect transpiration

Answer 15

The rate of transpiration increases and decreases depending on if the wind speed is increased or decreased

• if the airflow is high, water particles in the the outside of the leaf will be blown away quicker. This means that there will be rapid changes in the concentration gradient, and it will remain high

Question 16

How does humidity effect rate of transpiration

Answer 16

Humidity is the measure the rate of how much water is in the air at a given time

If there is a lot of water in the air, the concentration gradient will be low, meaning that transpiration will happen slowly,
If there is low humidity, there will be a high concentration gradient, which means that transpiration will go happen quicker

Question 17

Photosynthesis occurs in the guard cells but not the epidermal cells.
Explain why this is important in the control of the rate of transpiration in the plant.

4 marks

Answer 17

-> photosynthesis makes sugars in guard cells
-> epidermal cells dont photosynthesise so lower in sugar than guard cell
->epidermal cells higher water potential than guard cells
-> water enters guard cells by osmosis
-> increasing turgidity of guard cell opens stomata
-> opening / size of stoma affects transpiration rate

Question 19

Why is the inner cell wall of the guard cells thicker than the outer cell wall of the guard cells

Answer 19

Prevents the guard cells from expanding evenly, forcing the guard cells to develop a curved shale, helping the stoma open

Question 20

How do guard cells control opening of stomata

Answer 20

-> light levels trigger ions (such as K+ ions) to be transpferredd into the guards cells
-> increases concentration of the guard cells and lowers water potential of it
-> water moves into the guards cells via osmosis (area of high water potential to low water potential)
-> guard cells swell and become turgid

Question 21

Why do the guard cells have rings of cellulose

Answer 21

-> to stop the cell from expanding widthways and only letting it expand lengthways when water moves into it
-> means the stoma can open

Question 23

A student uses a simple potometer to study the effect of different temperatures on the cut shoot of a plant.
What does the potometer actually measure?

Answer 23

Volume of water taken up by shoot

Question 24

Sieve plates are found in plants
What is their location and function

Answer 24

Found in phloem and allow movement of sucrose

Question 25

Fanconi anaemia is a genetic disorder. It results in the bone marrow being destroyed. This causes a decrease in the numbers of red blood cells, white blood cells and platelets. Explain two possible symptoms of Fanconi anaemia.

Answer 25

-> tiredness due to lack of red blood cells -> project to infection due to lack of white blood cells -> slow blood clotting due to lack of platelets

Question 26

Describe what happens during transpiration

Answer 26

-> water evaporates on the surface of sponges mesophyll -> water diffuses through stomata pores

Question 27

Describe how Potometer scan be used to investigate the effect of light on transpiration rates

Answer 27

Can measure gas bubble movement over a specific amount of time, and see how that movement changes over varying distances

Question 28

Why is a heat sink used in Potometer

Answer 28

-> to absorb heat generated from lamp in order to stop it from changing the results -> heat may mean that the distances closer to the lamp have much higher transpiration rates then they should have due to increased KE of the particles

Question 29

Photosynthesis occurs in the guard cells but not the epidermal cells. Explain why this is important in the control of the rate of transpiration in the plant.

Answer 29

-> photosynthesis makes sugars -> guard cells have higher sugar concentrations than epidermal cells, because epidermal cells done photosynthesise but guard cells do -> guard cells there by have lower water potential than epidermal cells -> when high amounts of photosynthesis takes place water moves into guard cells due to differences in WP -> guard cells become turgid, amd due to the difference in thickness of cell walls, the stomata opens -> higher rate of transpiration

Question 30

When the outside of a plant, around the phloem is ringed, the part above is swollen Explain why

Answer 30

-> phloem in that section is removed due to the plant being ringed -> swelling caused by build up of sugar that can’t be transported -> (sugar produced in leaves)

Question 31

How do vascular bundles provide support in the stem

Answer 31

I’m the stem they are located around the outer edge, providing the stem with strength to resist bending in the wind -

Question 32

How do the vascular bundles provide support in the roots

Answer 32

in the root they are found in its centre, enabling the to act as an anchor - the root can bend as the plant moves in the wind