Transport In Plants

Question 0

What’s similar between animals and plants?

Answer 0

They are multicellular, plants could exchange substances by direct diffusion but that would be too slow so they have transport systems.

Question 1

What substances do plants need to live?

Answer 1

Water, minerals and sugar.

Question 2

What 2 tissues are involved in transport In plants?

Answer 2

Xylem and phloem

Question 3

What’s the role of the xylem?

Answer 3

Transports water and mineral ions, it also provided support.

Question 4

What’s the role of the phloem?

Answer 4

Transports dissolved substances, like sugars.

Question 5

In the root where are the xylem and phloem, and why?

Answer 5

They are In the centre to provide support to the root as it pushes through the soil.

Question 6

Where are the xylem and phloem in the stems and why?

Answer 6

Near the outside to provide ‘scaffolding’ to reduce bending.

Question 7

Where are the xylem and phloem In a leaf and why?

Answer 7

They make up a network of veins which support the thin leaves.

Question 8

What are xylem vessels?

Answer 8

The part oft he xylem that transports water and ions.

Question 9

Give three reasons how xylem vessels a re adapted to their function

Answer 9

They are long, tube like structures.
There are no end walls making an uninterrupted tube so water can easily pass through.
The cells are dead, they have no cytoplasm.
Their walls are thickened with lignin, this helps to support the vessels.

Question 10

Give one similarity and difference between xylem and phloem

Answer 10

They are both formed from cells arranged in tubes.

Phloem is just for transport, xylem is for transport and support.

Question 11

What does phloem contain?

Answer 11

Phloem fibres, phloem parenchyma, sieve tube elements and companion cells

Question 12

What’s are sieve tube elements?

Answer 12

They are in phloem tissue, they are living cells that form the tube for transporting solutes through the plant. The sieve parts are the end walls which have lots of holes in them to allow solutes to pass through.

Question 13

What’s unusual about sieve tube elements?

Answer 13

They are living cells with no nucleus, a very thin layer of cytoplasm and few organelles.

Question 14

What are companion cells?

Answer 14

A lack of nucleus and other organelles in sieve tube elements means that they can’t survive on their own so there is a companion cell for every sieve tube element. The companion cells carry out the living functions for both themselves and their sieve tube. They provide energy for active transport of solutes.

Question 15

How does water enter the plant?

Answer 15

Through it’s root hair cells.

Question 16

Water enters the root hair cells then passes …

Answer 16

Through the root cortex, including the endodermis to reach the xylem.

Question 17

Why is water drawn to the root?

Answer 17

Water moves from areas of high water potential to areas of low water potential. From a low concentration to a high concentration. The soil around the root has a high water potential and the root has a low water potential so water is taken up by the water potential gradient.

Question 18

What is the symplast path?

Answer 18

A method for water to travel from the root cortex to the xylem. Here is goes through the living parts of the cell ( the cytoplasm).

Question 19

What’s the apoplast path?

Answer 19

A method for water to travel from the root cortex to the xylem. It goes through the non living parts of the cells (cell walls).

Question 20

What’s the main pathway and why?

Answer 20

The apoplast pathway because it provides the least resistance.

Question 21

Xylem vessel transport water all round the plant, at the leaves what happens?

Answer 21

Water leaves the xylem and moves into the cells by the apoplast pathway. Water evaporates from the cell walls into the spaces between cells in the leaf. When the stomata open water moves out of the leaf.

Question 22

What’s a casparian strip?

Answer 22

It blocks the apoplast pathway.

Question 23

What are the mechanisms that help water move during the transpiration stream?

Answer 23

Cohesion , adhesion and tension

Question 24

How does cohesion and tension help water move up plants, from roots to leaves? (Transpiration stream)

Answer 24

Water evaporates from the leaves, this creates tension which pulls more water Into the leaf. Water molecules are cohesive so they follow each other. Therefore all of the water in the xylem moves upwards.

Question 25

How does adhesion help water move up plants, from roots to leaves? (Transpiration stream)

Answer 25

Water molecules are attracted to each other and the walls of xylem vessels, this helps water to rise In the vessels.

Question 26

What is transpiration?

Answer 26

The evaporation of water from a plants surface, especially the leaves.

Question 27

Plants need to ope their stomata to let carbon dioxide to photosynthesise, what problems does this cause?

Answer 27

It also let’s water out, there is a higher concentration of water inside the leave than on the outsides so it moves out. Transpiration Is a side effect of gas exchange.

Question 28

How does light affect the transpiration rate?

Answer 28

When it’s lighter outside the stomata open, so the lighter it is the faster the rate .

Question 29

How does temperature affect the transpiration rate?

Answer 29

The higher yeh temperature the faster the rate, warmer water molecules have more energy so they evaporate faster.

Question 30

How does humidity affect the transpiration rate?

Answer 30

The lower the humidity the faster the rate. If the air around is dry the water potential gradient is increased, this increases transpiration.

Question 31

How does wind affect the transpiration rate?

Answer 31

The more windy the faster the rate, lots of air movement blows away water molecules from the stomata. This increases the water potential gradient.

Question 32

What are the main factors effecting transpiration rates?

Answer 32

Wind, humidity, light and temperature

Question 33

What’s a potometer?

Answer 33

It estimates transpiration rates. It measure the uptake of water by a plant.

Question 34

How do potometers work?

Answer 34

Cut a shoot under water (to prevent air from entering them). Check that the potometer is full of water with no air bubbles. Put the shoot into the apparatus underwater so no air is entering them. Dry the leaves. Record the starting position of the air bubble, start a stop watch and record the distance moved.

Question 35

What are xerophytes?

Answer 35

Plants adapted to reduce water loss.

Question 36

Give some example of xerophytes?

Answer 36

Cacti and pine trees and prickly pears

Question 37

What is a xerophyte adaptation?

Answer 37

Stomata that’s re sunk in pits so that they are sheltered from the wind, this helps slow transpiration.
A layer of hairs on the epidermis, this traps moist air around the stomata slowing down transpiration.
Curled leaves lower the surface area for losing water.
Spines instead of leaves also reduce surface area for water loss
A thick waxy epidermis making it waterproof

Question 38

What’s translocation?

Answer 38

The movement of dissolved substances (sugars) to where they are needed in a plant. It moves substances from source to sink (source is where it’s made and sink is where it’s used up).

Question 39

Where does translocation occur?

Answer 39

In the phloem, it’s an active process.

Question 40

What’s the mass flow hypothesis

Answer 40

Scientist aren’t too sure how dissolved substances re transported from source to sink, this is a theory that best supports.

Question 41

Explain the mass flow hypothesis at the source end

Answer 41

Active transport loads the dissolved solutes into the sieve tubes in the phloem at the source (e.g. Leaves). This lowers the water potential so water enters by osmosis, this creates high pressure inside the sieve tubes by the source end of the phloem.

Question 42

Explain the mass flow hypothesis at the sink end

Answer 42

Solutes are removed from the phloem to be used up, this increase water potential inside the sieve tubes so water leaves by osmosis. The pressure lowers in the sieve tubes. The result is a pressure gradient from the source end to the sink end. This gradient pushes solutes along the sieve tubes to where they are needed.

Question 43

Give so e evidence for mass flow hypothesis

Answer 43

If you out a metabolic inhibitor into the phloem then translocation stops, this is evidence that scribe transport occurs.

Question 44

They is evidence against the mass flow hypothesis

Answer 44

The sieve plates would create a barrier to mass flow, a lot of pressure would be needed for the solutes to get through at a reasonable rate.