Brainscape's Knowledge GenomeTM

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


See full index

A level Biology - Regular > Chapter 9 - Transport in plants > Flashcards

Chapter 9 - Transport in plants Flashcards

1
Q

Why do plants need specialised transport systems ?

A

1 - Metabolic demand
2 - Size
3 - SA:V ratio

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

Explain why plants need specialised transport systems due to metabolic demand ?

A
  • Internal parts of the plant cannot photosynthesise
  • Hormones need to be transported
  • Mineral ions absorbed at the roots need to be transported to make required proteins for enzymes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Explain why plants need specialised transport systems due to size ?

A
  • Plants are too large to survive via only diffusion hence must have specialised transport systems
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Explain why plants need specialised transport systems due to SA:V ratio ?

A

Although leaves have a high SA:V ratio
The plant iteself have a low SA:V ratio and therefore need specialised exchange systems

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

What are the two types of Dicots ?
What are the features of each ?

A

1) Herbaceous Dicots
- Soft tissue
- Short life cycle
2) Woody dicots
- Hard lignified tissues
- Long life cycle

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

What specialised tissues do Dicot plants have to transport minerals and water ?

A

Vascular bundles

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

What are the features of vascular bundles ?

A
  • Distributed throughout the plant
  • Made of xylem and phloems
  • Provides structure
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Describe the vascular bundle structure in the stem

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

Describe the vascular bundle structure in the roots

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

Describe the vascular bundle structure in the leaf

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

What is the structure of the xylem ?

A
  • non living
  • Long hollow structures
  • Made up of columns of cells fused together
  • Spirals of lignin running around the lumen
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the structure of the xylem ?

A
  • non living
  • Long hollow structures
  • Made up of columns of cells fused together
  • Spirals of lignin running around the lumen
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the function of the xylem ?

A
  1. Transport of water and mineral ions
    • From the roots to the leafs
  2. Mechanical support
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the structure of the phloem ?

A
  • Living tissue
  • Main transporting vessles contain sieve tube elements
  • Cells joined end to end
  • Long and hollow structure
  • Not lignified Sieve plated between cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the function of the sueve plates ?

A
  • allow phloem contents to pass through
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are the features and functions of the companoin cells ?

A
  • Linked via plasmodesmata
  • life support system for sieve tube cells
  • Assist in atp production
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Why is water important in the transport of plants ?

A
  • Provides turgor pressure as a result of osmosis; creates a hydrostatic skeleton that supports stem and leaves
  • Loss of water via evaporation provides cooling
  • Ions and products of photosynthesis are transported into aqeuous solutions
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are the adaptations of root hair cells ?

A

1) Small size - penetrates soil
2) Large SA:V
3) Thin surface layer
4) High concentration of solutes within the cytoplasm to maintain a high water potential gradient

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What are the different pathways of water movement ?

A

1) Symplast
- Through cytoplasm
- Each one further away from roots has a lower water potential
2) Apoplast
- Through cell wall
- Water fills spaces between network fibres of cellulose cell wall
- Cell walls have open structure hence there is little to no resistance

20
Q

How does trasnportation across xylem occur ?

A

1 - Water moves through root hairs into apoplast and symplast pathway
2 - Water reaches endodermal layer
3 - Band of waxy material forms water proof layer on caspirian strip
4 - Water moves from apoplast to symplast because of this
5 - As water passes through the membrane toxins are lost
6 - Minerals within pumped into xylem results in root pressure which pushes water up the xylem

21
Q

What is the evidence for active transport in root pressure ?

A

1) Cyanide poisoning prevents production of ATP if cyanide is applied to roots, cells have no energy = no root pressure

2) Root pressure increases when temp increases suggesting chemical reactions are taking place

3) If O2 levels drop root pressure drop

22
Q

What are the features of plants that allow transpiration to occur ?

A
  • Leaves have a waxy cuticle that make them waterproof
  • Gas exchange works via stomata which are opened and closed via guard cells
23
Q

What is Cohesion-Tension theory ?

A
  • Water vaporises from the surface of mesophyll cells into air spaces of the leaves
  • This loss of water lowers water potential meaning water moves into the cell from adjacent cells via osmosis
  • This is repeated across the plant into the xylem and then into the leaf
24
Q

What is Cohesion-Tension theory ?

A
  • Water vaporises from the surface of mesophyll cells into air spaces of the leaves
  • This loss of water lowers water potential meaning water moves into the cell from adjacent cells via osmosis
  • This is repeated across the plant into the xylem and then into the leaf
25
Q

What is the evidence for cohesion-tension theory ?

A

1 - Change in diameter of trees during night and day hence as diameter decreases cohesion increases and so does tension
2 - When xylem vessels are cut and put underwater air is drawn up as oppose to water leaking out
3 - After xylem vessel is broken water can be no longer pulled up du eo tlack of cohesion

26
Q

What is used to control rate of transpiraton controlled ?

A

Stomatal pores - Turgor driven process

27
Q

How do stoma control rate of transpiration ?

A

When turgor pressure is low the asymmetric configuration of guard cell walls closes the pore

When environmental conditions are favourable - guard cells pump solutes into the stoma via active transport hence increasing turgor pressure and opening stomatal pores

28
Q

What factors affect transpiration ?

A

1 - Light intensity
More light = increased rate of photosynthesis
stomata will open more hence more diffusion of water vapour
2 - Relative humidity
More water vapour in the air means reduced water vapour potential gradient hence rate of transpiration decreases
3 - Temperature
Increase in temp = Increase in kinetic energy of water molecules and therefore increases the rate of evaporation from mesophyll cells into the air
Increase in temp increases conc. of water vapous in the air

29
Q

How does soil water availability affect rate of transpiration ?

A

If the soil is dry the plant will be under water stress hence the rate of transpiration will reduce

30
Q

Where do plants transport compounds from and to ?

A

organic compounds in the phloem are carried from source to sink - process is called translocation (Active process)

31
Q

What are assimilates ?

A
  • Products of photosynthesis that are carried around
32
Q

What are the main sources of assimilates ?

A
  • Green leaves and green stems
  • Storage organs such as tubers and tap roots
  • Food stores in seeds
33
Q

What are the main sinks in a plant ?

A
  • Roots are growing and/or actively absorbing mineral ions
  • Meristems that are actively dividing
  • Any parts of the plant that are laying down food stores
34
Q

What are the two ways phloem loading can occur ?

A

1 - Symplast route
2 - Apoplast route

35
Q

What are the features of the symplast phloem loading route ?

A
  • Sucrose from source moves through cytoplasm of mesophyll cells and on into the seive tubes by diffusion thorugh plasmodesmata
  • Largely a passive process
    Sucrose ends up in seive elements and water follows by osmosis
36
Q

What are the features of the apoplast phloem loading route ?

A
  • Through cell walls and inter cellular space to companion cells and sieve elements
  • Active process
37
Q

How does phloem loading via the apoplast route work ?

A

1 - Hydrogen ions are actively pumped out of the companion cell into the surrounding tissue using ATP
2 - Hydrogen ions return to the companion cell down a conc. gradient via a co-transport protein; increases sucrose conc. in companion cells and seive elements through plasmodesmata
3 - As a result of the build up of sucrose in the companion cell and sieve tube element, water also moves in via osmosis

38
Q

How are companion cells adapted for their function in apoplast phloem loading ?

A
  • Many infolds in their membranes to give increase SA for the active transport of sucrose into the cytoplasm
39
Q

What are the featrues of phloem unloading ?

A
  • Can happen at any point
  • Occurs due to diffusion
  • Sucrose rapidly moves on into other cells by diffusion or is converted into another substance so that conc. gradient is kept
40
Q

What is the evidence for translocation ?

A
  • Microscopes allow us to see adaptations of companion cells for active transport
  • If mitochondria of companion cells are poisoned translocation stops
  • Flow of sugars in phloem is 10,000 times faster than if it was by diffusion alone
41
Q

What are xerophytes ?

A
  • Plants in dry/icy conditions
  • Must maximise water conservation
42
Q

What are the adaptations of xerophytes ?

A
  • Thick waxy cuticle to prevent water loss and make itself waterproof
  • Sunken stomata to reduce air movement so traps moist air
  • Reduced number of stomata
  • Hairy leaves to trap humidity
  • Curled leaves to reduce SA hence reduces transpiration rate
  • Succulents which means it stores water in parenchyma tissue in stems and roots
  • Reduced number of leaves to minimise water loss
  • Long tap roots to penetrate soil
43
Q

What are hydrophytes ?

A

Plants in wet freshwater environments
Adapt to excess water

44
Q

What are the adaptations of hydrophytes ?

A
  • No/Thin waxy cuticle layer to increase water loss
  • Always open stomata
  • Reduced structure with no stems
  • Small roots so water diffuses directly into stem
  • Large SA of stems and roots to maximise area for photosynthesis
  • Air sacs to allow leafs to float
45
Q

What are Aerenchyma and why are they adaptations for hydrophytes ?

A
  • Large air spaces
  • Makes leaves and stems more buoyant
  • Low resistant pathway for O2

A level Biology - Regular (14 decks)

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