Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

A-level Biology > 3.1.3 - Transport in plants > Flashcards

3.1.3 - Transport in plants Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

What are the three main reasons for why transport systems are needed in multicellular plants ?

A
  • Metabolic demand
  • Size
  • Surface area to volume ratio
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Explain why multicellular plants require transport systems due to metabolic demand ?

A
  • Glucose and oxygen need to pass around the plants to places that don’t photosynthesise ( eg. Roots )
  • Waste products need to be removed
  • Hormones must be transported to areas where they have effect
  • Mineral ions absorbed by roots need to be transported to all cells to synthesise proteins
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Explain why multicellular plants require transport systems due to size ?

A
  • Many plants grow throughout their lives and become quite large
  • This means there’s a long distance from external surface to cells
  • So, effective transport systems are required to move substances both up and down big plants from tips of roots to topmost leaves/ stems
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Explain why multicellular plants require transport systems due to surface area to volume ratio ?

A
  • Many plants have a small SA : V ratio so cannot solely rely on diffusion and osmosis since it is not fast enough/ sufficient
  • Therefore effective transport systems are required to ensure molecules/ substances required reach all cells/ tissues
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is a dicotyledon?

A

A flowering plant with an embryo that bears two catyledons ( seed leaves )

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the two types of dicotyledons ?

A
  • herbaceous
  • Woody
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is another name for a dicotyledon?

A

Dicot

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the transport system in herbaceous dicots ?

A
  • Plants have a series of transport vessels running through the stem, roots and leaves known as the vascular system
  • In herbaceous dicots, the vascular system is made up of the xylem and the phloem which are arranged in vascular bundles
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Where are vascular bundles found in herbaceous dicots ?

A
  • Leaves
  • Stems
  • Roots
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Explain how vascular bundles are arranged in the stem ?

A

In the stem, the vascular bundles are around the edge
- This provides strength and support to stem

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Draw how vascular bundles are arranged in the stem ?

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Explain how vascular bundles are arranged in the roots ?

A
  • In the roots, the vascular bundles are in the middle
  • This helps the plant withstand the tugging strain of stem/leaves being blown in the wind
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Draw how vascular bundles are arranged in the roots ?

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Explain how vascular bundles are arranged in the leaves ?

A
  • In the leaves, the vascular bundles are found in the midrib of the leaf
  • This helps support the structure of the leaf
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Draw how vascular bundles are arranged in the leaves ?

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What does the xylem do ?

A
  • The xylem transports water and mineral ions from the roots to the shoots of the plant
  • It also provides structural support
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Explain the structure of the xylem / its adaptations ?

A
  • Xylem tubes are made of dead cells called xylem vessels ( long hollow structures made by several columns of cells fusing end to end )
  • Xylem vessels are surrounded by the thick-walled xylem parenchyma
  • Xylem vessels are reinforced by a woody substance called lignin
  • Unlignified areas are called bordered pits
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What does the xylem parenchyma do ?

A
  • The xylem parenchyma stores food and contains tannin deposits
  • Tannin is a bitter chemical that acts as a chemical defence, protecting plant from herbivores
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What does lignin do ?

A
  • It provides extra mechanical strength to the xylem vessels
  • This ensures they don’t collapse under the transpiration pull
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What happens at the unlignified arrears of the xylem/ bordered pits ?

A

This is where water leaves the xylem and moves into other cells of the plant/ lateral movement of water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What does the phloem do ?

A

The phloem supplies amino acids and sugars from where they are made ( in leaves via photosynthesis ) to where they are required by the plant

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Explain the structure of the phloem/ its adaptations ?

A
  • Phloem is made up of severe tube elements ( many cells joined end to end forming long hollow structures )
  • Phloem tubes are not lignified
  • Between sieve tube elements, walls are perforated forming sieve plates
  • Sieve tube elements are closely linked to companion cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What do the sieve plates do ?

A

They allow phloem content to flow through the phloem

24
Q

What do companion cells do ?

A

They function as a ‘life support system’ for the sieve tube cells, carrying out the living function

25
Q

Draw a diagram of the xylem and the xylem parenchyma ?

A
26
Q

Draw a diagram of the phloem ?

A
27
Q

Describe procedure that could be used to observe the position of xylem vessels in various areas in the plant ?

A
  • Put the section of the plant ( leaf, stem, roots ) in dye/ stain
  • Cut it transversely producing a cross-section
28
Q

Explain the movement of water into roots ?

A

-Water is taken into the plant via root hair cells in the soil
- Soil water has a low concentration of dissolved minerals so a high water potential
- Cytoplasm ad vascular sap in cell contain numerous solvents resulting in low water potential
- This leads water to enter root hair cell via osmosis

29
Q

What are the adaptations of root hair cells as exchange surfaces ?

A
  • They are small in size ( allowing them to penetrate between soil particles easily )
  • They have a large SA : V ratio due to root hairs/ extensions
  • Thin surface area
  • Maintained concentration gradient ( concentration of solutes in cytoplasm is maintained )
30
Q

What are the two pathways of water moving through the xylem ?

A
  • The symplast pathway
  • The apoplast pathway
31
Q

Define the term ‘symplast pathway’ ?

A

Symplast pathway : The continuous cytoplasm of the living plant cells that is connected through the plasmodesmata

32
Q

Define the term ‘apoplast pathway’ ?

A

Apoplast pathway : the cell walls and the intercellular spaces

33
Q

Explain how water moves through the symplast pathway ?

A
  • Water moves through the symplast via osmosis
  • Due to water entering root hair cells via oasis from the coil, it will have a more dilute cytoplasm and therefore a higher water potential than the next adjacent cell
  • This will cause water to move via osmosis from cell to cell repeatedly until the xylem is reached
  • When water leaves the root hair cell, water potential of cytoplasm drastically falls maintaining a steep concentration gradient ensuring as much water as possible continues to move
34
Q

Explain how water travels through the apoplast pathway ?

A
  • Water fills the spaces in cellulose cell wall
  • Water molecules form chains due to cohesive force
  • As water moves into the xylem, more water molecules are pulled through by polar and cohesive forces creating a continuous flow of water through cellulose cell wall which offers minimal resistance
35
Q

What is a casparian strip ?

A

A band of waxy material that runs around each of the endodermal cells forming a waterproof layer

36
Q

What is the role of the casparian strip in transpiration ?

A
  • The strip is impervious to water/ solutions
  • This forces water in the apoplast pathway to move into the cytoplasm joining the symplast pathway across the plasma membrane
37
Q

What is the endodermis ?

A

Layer of cells surrounding vascular tissue of roots

38
Q

Describe and explain the movement of water into the xylem ?

A
  • Water moves through the roots via the apoplast and symplast pathways until it reaches the endodermis
  • Due to the casparian strip, water in apoplast pathway cannot move further and is forced into the cytoplasm joining the symplast pathway
  • This causes water to pass through selectively permeable membrane which removes any toxic solutes from soil water preventing it from reaching living tissue
  • Water potential of endodermal cells is higher than xylem cells due to dilute solute concentration in cytoplasm as well as mineral ions being pumped into xylem cells from endodermal cells via active transport
  • This increases rate of water moving into xylem via osmosis
39
Q

What happens once water enter the xylem ?

A
  • Once inside xylem, water returns to apoplast pathway to enter xylem itself and move up the plant
  • Movement of mineral ions into xylem via active transport creates root pressure which gives water a push up the xylem
40
Q

Define the term ‘transpiration’ ?

A

Transpiration - The loss of water vapour from the stems and leaves of a plant as a result of evaporation from cell surfaces inside the leaf and diffusion down the concentration gradient out through the stomata

41
Q

Explain why water is cohesive ?

A

Water forms hydrogen bonds with carbohydrates in the walls of narrow xylem vessels

42
Q

Explain why water is adhesive ?

A

Water molecules form hydrogen bonds with each other causing them to stick together

43
Q

Describe the process of transpiration ?

A

1 ) Water molecules evaporate from the surface of the mesophyll cells into the air spaces in he leaf and move out of the stomata into surrounding air via diffusion down the concentration gradient
2 ) Loss of water causes water potential in mesophyll cells to lower, causing water from an adjacent cell to move into the cell along the symplast and apoplast pathways
3 ) Repeated across leaf until the xylem where water moves out of xylem into cells of leaf via osmosis
4 ) The combined effect of adhesion and cohesion of water results in water exhibiting capillary action
5 ) This causes water to be drawn up the xylem in a continuous stream to replace water lost via transpiration which is called the transpiration pull
6 ) Transpiration pull results in tension in the xylem which helps to move water across roots from soil

44
Q

What does it mean when water exhibits capillary action ?

A

It is the process by which water can rise up a narrow tube against the force of gravity

45
Q

What is the model of water moving from soil in a continuous stream up the xylem and across the leaf called ?

A

The cohesion-tension theory

46
Q

What is the evidence for the cohesion-tension theory ?

A
  • When a xylem vessel is broken air is drawn in to the xylem rather than water leaking out
  • Changes in the diameter of a tree
47
Q

Explain how the changing diameter of a tree serves as evidence for the cohesion-tension theory ?

A
  • When transpiration is at its height during the day, the tension in the xylem vessels is at its highest too
  • As a result the tree shrinks in diameter.
  • At night, when transpiration is at its lowest, the tension in the xylem vessels is at its lowest and the diameter of the tree increases
48
Q

Explain why air being drawn into the xylem instead of letting water leak out serves as evidence for the cohesion-tension theory ?

A
  • If a xylem vessel is broken and air is pulled in, the plant can no longer move water up the stem
  • This is because the continuous stream of water molecules held together by cohesive forces has been broken
  • Therefore, transpiration delivers water
49
Q

What are the factors affecting the rate of transpiration ?

A
  • Light intensity
  • Relative humidity
  • Temperature
  • Air movement
  • Soil-water availability
  • Stomata
50
Q

Explain how the effect of relative humidity on the rate of transpiration ?

A
  • As the humidity increases, the air is saturated with more water vapour
  • This means the concentration gradient is weaker
  • Therefore less water is lost via transpiration decreasing the rate
51
Q

Explain how the effect of light intensity on the rate of transpiration ?

A
  • As light intensity increases, the rate of transcription increases
  • Guard cells are responsive to Light intensity
  • Therefore, when it is high they become turgid and the stomata open, allowing water to be lost via transpiration
52
Q

Explain how the effect of temperature on the rate of transpiration ?

A
  • As the temperature increases, the kinetic energy of particles increases
  • Therefore, water molecules move faster and evaporate from the mesophyll and diffuse at a faster rate
  • This results in an increased rate of transpiration
53
Q

Explain how the effect of air movement on the rate of transpiration ?

A
  • Air movement removes water vapour from the air surrounding the Leaf
  • This creates a stepper concentration gradient between the leaf and the surrounding air
  • This causes more water to be lost via transpiration
54
Q

Explain how the effect of soil-water availability on the rate of transpiration ?

A
  • If the soil is very dry/ there is not a lot of water present the plant will be under stress
  • This will cause the water potential of the plant to decrease meaning the rate of diffusion will decrease
55
Q

Explain how the effect of stomata on the rate of transpiration ?

A
  • Stomata can be opened or closed depending on the conditions the plant is in ( light intensity and water potential )
  • As the number of stomata increases, more water is lost via transpiration leading to an increased rate

A-level Biology (30 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions