Brainscape's Knowledge GenomeTM

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


See full index

Z A level Biology > Transport in plants > Flashcards

Transport in plants Flashcards

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

Why are transport systems needed?

A
  1. To move substances from where they are absorbed to where they are needed, e.g. water and ,mineral ions are absorbed by roots and transported in the xylem to other parts of the plant
  2. To move substances from where they are produced to where they are needed for metabolism
    - E.G. sugars are produced in leaves, but glucose is needed by all parts of the plant for respiration and for converting to cellulose for making cell walls in areas of growth. Glucose can be moved in phloem as part of the sucrose molecule
  3. To move substances to a different part of the plant for storage
    - E.G to move sugars into a potato tube for storage in the form of starch
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Why is carbon dioxide needed?

A
  1. Photosynthetic plants cells require a supply of carbon dioxide during daylight and most photosynthetic tissue is in leaves
  2. Most plants have evolved thin flat leaves with surface area ideal for absorbing as much carbon dioxide as possible
  3. They obtain this by diffusion from the air
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Why is oxygen needed?

A
  1. All plants require a supply of oxygen for respiration, but cells which are actively photosynthesising produce more than enough oxygen for their own needs because oxygen is a waste product of photosynthesis
  2. Cells which are not photosynthesising need to take in oxygen form their environment
  3. Plants have much lower energy demands than animals, so they respire at much lower rates
  4. They therefore do not need such a rapid supply of oxygen
  5. The branching shape of plants and a network of air spaces in the plant body provide a large enough surface area for effective absorption of oxygen by diffusion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Summarie plant transport

A
  1. Easy for carbon dioxide and oxygen to diffuse into and out of the bodies of pants, reaching and leaving every cell quickly enough down diffusion gradients
  2. Therefore no need for a transport system of these gases
  3. Transport systems needed for distribution of water, inorganic and organic nutrients as well as other substances such as plant hormones
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What does xylem do?

A
  1. Carries mainly water and inorganic ions (mineral salts from roots to the parts above ground)
  2. The xylem sap contained in the xylem can move in only one direction, from the roots to rest of the plant
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the phloem?

A
  1. Carries substances made by photosynthesis from the leaves to other areas of the plant
  2. At any one time, phloem sap can be moving in different directions in different parts of the phloem
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What happens in neither the xylem or phloem?

A
  • Fluids move as rapidly as blood does in mammal, nor is there any obvious pump such as the plant
  • Neither plant transport system carries oxygen or carbon dioxide which travel to and from the cells and their environment by diffusion alone
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are the main organs improved of transport in plants?

A

stems roots and leaves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are organs and tissues?

A
  1. Organs are composed of more than one tissue
  2. Tissues are collections of cells specialised for a particular function
  3. The cells may be of the same type, such as parenchyma, or of different types such as xylem and phloem
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What can flowering plants (angiosperms) be?

A
  1. Monocotyledons (monocots)

2. Dicotyledons (dicot)

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

Describe monocotyledons

A

E.G grasses have long narrow leaves

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

Describe dicotyledons

A

Leaves with blades and stalks (petioles)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is same and different monocotyledons and dicotyledons?

A
  • The mechanisms of transport through both types of plant are the same
  • Differences in the distribution of xylem and phloem in their roots, stems and leaves
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Describe the epidermis

A
  1. A continuous layer on the outside of the plants, one cell thick that provides protection
  2. In stems and leaves it is covered with a waxy cuticle
  3. In leaves it also has pores, called stomata
  4. In roots it may have extensions called root hairs
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is a waxy cuticle?

A

Waterproof and helps to protect the organ from drying out and infection

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

What are the stomata?

A

Pores which allow entry of carbon dioxide for photosynthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are root hairs?

A

Extensions to increase the surface area for absorption of water and mineral salts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is parenchyma?

A
  1. Made up of thin-walled cells used as packing tissue
  2. The cells are very metabolically active and may be used for many functions
  3. Air spaces between the cells allow gas exchange
  4. Water and mineral salts are transported through the walls and through the living contents of the cell
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What happens when the parenchyma cells are turgid (fully inflated with water)?

A

They help to support the plant, preventing wilting

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the function of parenchyma cells?

A

Used for storage of foods like starch

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

What does parenchyma form?

A

-The cortex in roots and stems, and piths in stems

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

What is the cortex?

A

The outer region of cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is the pith?

A

Is made up of similar cells, but the name given to the central region of stems

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What else does parenchyma contain?

A

Chloroplasts in leaves, where it is modified to form the palisade and spongy mesophyll

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What is the collenchyma?

A
  1. A modified form of parenchyma with extra cellulose deposited at the corners of the cells
  2. This provides extra strength
  3. The midrib of leaves contains collenchyma
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What is the endodermis?

A
  1. The endodermis, like the epidermis, is one cell thick

2. It surrounds the vascular tissue in stems and roots

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What is the mesophyll made up of?

A
  • Specialised parenchyma cells found between the lower and upper epidermis of the leaf
  • They are specialised for photosynthesis and therefore contain chloroplasts
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What are the two types of mesophyll?

A
  1. Palisade mesophyll (column shaped)
  2. Spongy mesophyll (in three dimensions it is spongy in appearance because it has many large air spaces between the cells)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What is another difference between spongy and palisade mesophyll?

A
  • Palisade mesophyll cells are near the upper surface of the leaf where they receive more sunlight
  • They therefore contain more chloroplasts than spongy mesophyll cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Describe the pericycle

A
  • A layer of cells, one to several cells thick, just inside the endodermis and next to the vascular tissue
  • It roots it is one cell thick and new roots can grow from this layer
  • In stems it is formed from a tissue called, sclerenchyma
  • This has dead, lignified cells for extra strength
31
Q

What is the vascular tissue?

A
  • Xylem and Phloem both contains more than one type of cell and together they make the vascular tissue
  • ‘Vascular’ ends having tubes for transporting fluids
32
Q

What does the xylem contain? What do the walls of cells contain?

A
  1. Xylem contains tubes called vessels made from dead cells called xylem vessel elements
  2. The walls of the cells are reinforced with a strong, waterproof material called lignin
33
Q

What does xylem allow?

A
  • Xylem allows long distance transport of water and mineral salts
  • It also provides mechanical support and strength
34
Q

Where is the xylem and phloem found?

A
  • The xylem, in roots is at the centre and has a series of ‘arms’ between which the phloem is found
  • In stems the xylem and phloem are found in vascular bundles
35
Q

Describe vascular bundles

A
  1. The outsides of these bundles have caps made of sclerenchyma fibres which provide extra support for the stem
  2. Sclerenchyma fibres, like xylem vessel elements, are long, dead, empty cells with lignified walls
  3. Unlike, xylem however they only have a mechanical function and do not transport water
36
Q

Describe the water movement of water through leaf

A
  1. Water vapour diffuses from an air space through an open stoma, a process called transpiration. It is carried away from the leaf surface by air movements. This reduces the water potential inside the leaf
  2. Water evaporates from a mesophyll cell wall into the air space
  3. Water moves through the mesophyll cell wall or out of the mesophyll cytoplasm into the cell wall
  4. Water leaves a xylem vessel through a non-lignified area such as a pit. It may enter the cytoplasm or cell wall of a mesophyll cell
  5. Water moves up the xylem vessels to resale the water lost from the leaf
    - Water is, in effect, being pulled through the plant as a result of transpiration and evaporation. Movement of water through the plant is therefore known as the transpiration stream
37
Q

What are the factors affecting transpiration?

A
  1. Humidity
  2. Wind speed and temperature
  3. Light intensity
  4. Very dry conditions
38
Q

How does humidity affect transpiration?

A
  • If the water potential gradient between the air spaces in the lead and the air outside becomes steeper the rate of transpiration will increase
  • In conditions of low humidity, the gradient is steep, so transpiration takes place more quickly than in high humidity
39
Q

How does wind speed and temperature affect transpiration?

A

-Transpiration may be increased by an increase in wind speed or rise in temperature

40
Q

How does light intensity affect transpiration?

A
  1. In most plants stomata open spring the day and close at night
  2. Most transpiration takes place through the stomata (although a little water vapour can escape through the epidermis if the cuticle is thin), so the rate of transpiration is almost zero at night
  3. Stomata mist be one during the day to allow carbon dioxide to diffuse into the leaf for photosynthesis
  4. This inevitably increases the rate of transpiration
  5. Closing at night, when photosynthesis is impossible,, reduces unnecessary water loss
41
Q

How do very dry conditions affect transpiration?

A

In especially dry conditions, when the water potential gradient between the internal air spaces and the external air is steep, a plant may have to compromise by partially or completely closing its stomata to prevent its leaves drying out, even if this means reducing the rate of photosynthesis

42
Q

How do hot conditions affect transpiration?

A
  1. In hot conditions, transpiration plays an important role in cooling the leaves
  2. As water evaporates from the cell walls inside the lead it absorbs heat energy from these cells, thus reducing their temperature
43
Q

What happens if the rate at which water vapour is lost by transpiration exceeds the rate at which a plant can take up water from the soil?

A
  • The amount of water in its cells decreases
  • The cells become less turgid and the plant wilts as the soft parts such as leaves lose their support provided by turgid cells
  • In this situation the plant will also close its stomata
44
Q

What are xerophytes?

A
  • Xerophytes (or xerophytic plants), are plants that live in places where water is in short supply
  • Many xerophytes have evolved special adaptations of they leaves that keep water loss down to a minimum
45
Q

What are some adaptations of xerophytes?

A
  1. Leaves can roll up die to shrinkage of special ‘hinge cells’
  2. Thick waterproof cuticle to the air outside the leaf, the cuticle contains a fat, relatively waterproof substance called cutin
  3. The stomata are found only in the upper epidermis and therefore open into the enclosed, humid space in the middle of the roll
  4. Hairs help to trap a layer of moist air close to the leaf surface, reducing the steepness of the diffusion gradient for water vapour
  5. The leaves are reduced to spines, which lessens the surface area from which transpiration can take place and protects the plants from being eaten by animals
  6. Trichomes which are tiny hair-like structures that act as a physical barrier to the loss of water, like the marram grass hairs
46
Q

How does water move from xylem across the leaf?

A
  1. As water evaporates from the cell walls of mesophyll cells more water is drawn into the walls to replace it
  2. This water comes from the xylem vessels in the leaf
  3. Water constantly moves out if these vessels through the undignified parts of the xylem vessel walls
  4. The water then moves down a water potential gradient from cell to cell in the leaf along two possible pathways
47
Q

What are the two possible pathways?

A
  1. Symplastic pathway, water moves from cell to cell via the plasmodesmata
  2. Apoplastic pathway, water moves through the cell walls
48
Q

Describe xylem vessels

A
  1. They are made from cells joined end to end to form tubes
  2. The cells are dead
  3. The walls of the cells are thickened with. hard, strong material called lignin
49
Q

What is the function of the xylem?

A
  1. Support and transport
    - It contains several different types of cell
    - In flowering plants, xylem tissue contains vessel elements, tracheids, fibres and parenchyma cells
50
Q

What are vessel elements and tracheids?

A
  • The cells that are involved with the transport of water

- Unlike other plants, flowing plants rely mostly on the vessel elements for their water transport

51
Q

What are sclerenchyma fibres?

A
  • Elongated cells with lignified walls that help to support the plant
  • They are dead cells, they have no living contents at all
52
Q

What are vessels made up of?

A
  • Many elongated cells called vessel elements arranged end to end
  • Each vessel element begins life as a normal plant cell in whose wall lignin is laid down
  • As lignin builds up around the cell, the contents of the cell die, leaving a completely empty space or lumen inside
  • However in those parts of the original cell walls where groups of plasmodesmata are found, no lignin is laid down
53
Q

What is lignin?

A

-Lignin is very hard strong substance which is impermeable to water (wood is made of xylem and gets its strength from lignin)

54
Q

What are these non-lignified areas?

A

-They can be seen as fans in the tick walls of the xylem vessel and are called pits

55
Q

What are pits?

A
  1. Not open pores
  2. They are crossed by permeable unthickened cellulose cell wall
  3. The pits in one cell link with those in neighbouring cells, so water can pass freely from one cell to the next
  4. The need walls of neighbouring vessel elements break down completely to form a continuous tube rather like a drainpipe running through the plant
  5. This long non-lying tube is a xylem vessel and it may be up to several meters long
    - The structural features of xylem vessels are closely related to their function
56
Q

What does the removal of water from the xylem vessels in the leaf do?

A

Reduces the hydrostatic pressure in the xylem vessels

57
Q

What is hydrostatic pressure?

A

The pressure extorted by a liquid

58
Q

How is the hydrostatic pressure affected?

A
  1. The hydrostatic pressure at the top of the xylem vessel becomes lower than the pressure at the bottom
  2. This pressure difference causes water to move up the xylem vessels in continuous columns
    - The higher pressure at the bottom pushes water up the straw
59
Q

What happens if the hydrostatic pressure is lower?

A

The lower the hydrostatic pressure, the lower the water potential, so a hydrostatic pressure gradient is also a water potential gradient

60
Q

How can you compare the water in the xylem vessels?

A
  • The water in the xylem vessels, like the liquid in a ‘sucked’ start is under tension
  • If you suck hard on the straw, its walls may collapse inwards as a result of the pressure differences you are creating
61
Q

How are the xylem dated to avoid the walls collapsing inwards?

A

Xylem vessels have stein, lignified walls to stop them from collapsing in this way

62
Q

Describe the movement of water up through the xylem vessels

A
  1. Mass flow
  2. This means that all the water molecules, (and any dissolved solutes) move together as a body of liquid like water in a river
63
Q

How is mass flow helped?

A
  1. The water molecules are attracted to each other by hydrogen bonding and this attraction is called cohesion
  2. They are also attracted to the cellulose and lignin in the walls of the xylem vessels, and this attraction is called adhesion
64
Q

Why is cohesion and adhesion important?

A
  • Cohesion and adhesion help to keep the water in a xylem vessel moving as a continuous column
  • The vessels are full of water
  • The fact that the cells are dead is an advantage because it means that there is no protoplasm to get in the way of transport
65
Q

What happens if there is an air bubble in the vessel?

A
  1. If an air bubble forms in the column, the column of water breaks and the difference in pressure between the water at the top and the water act the bottom cannot be transmitted though the vessel (there is an air lock)
  2. The water stops moving upwards
66
Q

How are air locks prevented?

A
  1. The small diameter of the xylem vessels helps to prevent such breaks from occurring
  2. The pits in the vessel walls allow water to move out into neighbouring vessels and so bypass such an air lock
  3. Air bubbles cannot pass through pits
  4. Pits are also important because they allow water to move out of xylem vessels surrounding living cells
67
Q

How is xylem and sclerenchyma different?

A
  • The distribution of these strengthening tissues is different roots and stems
  • This reflects the fact that these organs are subjected to different stresses and strains
    1. E.G Stems, need to be supported in air, whereas roots are usually spreading through soil and are subjected to pulling strains from the parts above the ground
    2. E.G In roots and stems of trees and shrubs extra xylem is made, forming wood
68
Q

What does phloem contain?

A
  1. Phloem contains tubes called sieve tubes made from living cells called sieve tube elements
  2. These allow long distance transport of organic compounds, particularly the sugar sucrose
69
Q

Describe transpiration

A
  1. The energy of the sun causes water to evaporate from the leaves, a process called transpiration
  2. This reduces the water potential on the leaves and sets up a water potential gradient throughout the plant
  3. Water moves down this gradient from the soil into the plant e.g. through its roots hairs
  4. Water then moves actress the root into the xylem tissue in the centre
  5. Once inside the xylem vessels, the water moves upwards through the root to the stem and from there into the leaves
70
Q

How does mesophyll relate to transpiration?

A
  1. The cells in the mesophyll layers are not tightly packed, and have many spaces around them filled with air
  2. The walls of the mesophyll cells are wet, and some of this water evaporates into the air spaces, so that the air inside the lead is usually saturated with water vapour
71
Q

What is the role of the stomata?

A
  1. The air in the internal spaces of the leaf has direct contact with the air outside the lead, through small pores called stomata
  2. If there is a water potential gradient between the air inside the leaf (higher water potential) and the air outside (lower water potential), then water vapour will diffuse out of the leaf down this gradient
  3. Although some of the water in the leaf will be used, e.g. in photosynthesis, most eventually evaporates and diffuses out of the lead by the process of transpiration
    - The distribution of stomata in the epidermis of leaves can be seen exposing ‘epidermal peels’ or ‘epidermal impressions’
72
Q

What is the definition of transpiration?

A

Transpiration is the loss of water vapour from a plant to its environment, by diffusion down a water potential gradient; most transpiration takes place through the stomata in the leaves

73
Q

How are leaves adapted to reduce rate of transpiration?

A
  1. Stomata close for longer during the day/when hot/when dry
  2. Stomata in pits
  3. Stomata only on lower surface of lead
  4. Trichomes
  5. Fewer stomata per unit area
  6. Thicker cuticle
  7. Reflective cuticle
  8. Thicker epidermis
  9. Curled leaves
74
Q

What are advantages of chloroplast movement within palisade cells?

A
  • Absorb more light

- Avoid damage by high light intensities

Z A level Biology (15 decks)

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