Transport In Plants Flashcards
1
Q
Why do plants need a transport system
A
All living things need to take substances from and return wastes to their environment
- larger plants have a smaller surface area to volume ratio
2
Q
What do plants use transport systems for
A
- move water and minerals from the roots up to the leaves
- move sugars from the leaves to the rest of the plant
3
Q
What are the vascular tissues
A
- xylem
- phloem
4
Q
What does the xylem do
A
Transport water and mineral ions up the plants
5
Q
What does the phloem do
A
Transports assimilates (sugars) up or down the plant
6
Q
What are dicotyledonous plants
A
Plants that have two seed leaves
7
Q
Where is the vascular bundle found in young roots
A
The center core
- shape of an X
8
Q
Where are the phloem in young roots
A
In between the x shape
9
Q
Where is the vascular bundle in stems
A
Near the outer edge of the step
10
Q
Where is the xylem in the vascular bundle of stems
A
On the inside
11
Q
What is in between the phloem and xylem in stems
A
Cambium
12
Q
What is the cambium
A
A layer of meristem cells that divide to produce new xylem and phloem
13
Q
What do xylem tissue consist of
A
- vessels to carry the water and dissolved mineral ions
- fibres to help support the plant
- living parenchyma cells which act as packing tissue to separate and support the vessels
14
Q
What does lignin do
A
Impregnates the walls of the xylem cells
- makes the walls waterproof
15
Q
What are the cells in xylem like
A
- lignin kills the cells
- end walls and contents of cells decay
- long column of dead cells with no contents
- xylem vessels
16
Q
What are pits
A
Allow water to leave one vessel and across into the next vessel
- latterly
17
Q
What are the adaptations of xylem
A
- made from dead cells aligned end to end to form continuous columns
- tubes are narrow, water column does not break easily and capillary action can be effective
- pits in the walls allow water to move sideways from one vessel to another
- lignin develops in spirals to allow them to bend and stretch
18
Q
How is the flow of water not impeded in xylem
A
- there are no cross-walls
- there are no cell contents, nucleus or cytoplasm
- lignin thickening prevents the walls from collapsing
19
Q
What does sucrose dissolved in water make in plants
A
Sap
20
Q
What are sieve tubes made of
A
- sieve tube elements
- companion cells
21
Q
What are sieve tube elements
A
- elongated sieve tube elements are lined up ene to end to form sieve tubes
- contain no nucleus and very little cytoplasm
- leaves space for mass flow of sap to occur
22
Q
What are sieve plates
A
- perforated cross-walls
- allows movement of sap from one element to the next
23
Q
What are companion cells
A
- small cells
- large nucleus
- dense cytoplasm
- numerous mitochondria (ATP needed for active processes)
- carry out metabolic processes
24
Q
What is plasmodesmata
A
Small gaps between cells
- cytoplasm flows between cells
25
What is the apoplast pathway
Water passes through the spaces in the cell walls and between cells
- doesn’t pass through cytoplasm
- water moves by mass flow
- stoped by casparian strip
26
What is the symplast pathway
Water enters the cytoplasm through the plasma membrane
- passes through the plasmodesmata
27
What is water potential
The tendency of water molecules to move from one place to another
28
What happens to water potential if high concentration
Low water potential
29
What direction does water move along water potential
From high to low
- down gradient
30
What is transpiration
The evaporation and diffusion of water out of the stomata
31
What is the pathway of water leaving through the leaf
- water enters the leaf through the xylem
- enters cells by osmosis or apoplast pathway
- water evaporates from the cell walls of the spongy mesophyll
- water vapour moves by diffusion out of the cell
32
Similarities between phloem and xylem
- cells joined end to end
- made of multiple cell types
- complex tissues
33
Differences between phloem and xylem
- x lignified, p not
- x continuous and hollow, p sieve plates
- x no companion cells, p do
- x have pits, p do not
34
What does the movement of transpiration do
- transports useful mineral ions up the plant
- maintains cell turgidity
- supplies water for growth, cell elongation and photosynthesis
- supplies water that, as it evaporates, can keep the plant cool of a hot day
35
How does light intensity effect transpiration rates
In light
- stomata open to allow gaseous exchange
- higher light intensity increases transpiration rates
36
How does temperature effect transpiration rates
Higher temperature
- increase rate of transpiration
- increase rate of evaporation
- increased rate of diffusion
- decrease the relative water vapour potential in the air
37
How does humidity effect transpiration rates
- higher relative humidity will decreases the rate of water loss
- smaller water vapour potential gradient
38
How does air movement affect rate of transpiration
- air movement out of the leaf will carry away water vapour
- maintains a high water vapour potential gradient
39
How does water availability affect transpiration rates
- little water in soil, plant cannot replace the water it lost
- if too little water stomata close and plant wilts
40
How does water flow up the plant
Through the xylem by mass flow
41
What is root pressure
Small pressure pushing water a short way up the xylem
42
What is adhesion in the stems
Water attaches to other water molecules and surfaces due to hydrogen boning
43
What is cohesion in the stem
Water attaches to other water molecules due to hydrogen bonding
44
What is transpiration pull
The loss of water by evaporation from the leaves must be replaced by water coming up the xylem
- forces of cohesion
45
What must plants on land be adapted to
- reduce loss of water
- replace water that has been lost
46
Structural and behavioural adaptation that terrestrial plants have done to prevent water loss
- waxy cuticle reduces evaporation of water
- stomata are found on the bottom of the leaves
- stomata are closed at night
- lose their leaves during the winter
47
What is a xerophyte
Plants that have adapted to live in very dry conditions
48
How have xerophytes adapted to their conditions
- leaf is rolled so that air is trapped inside
- thick waxy cuticle
- stomata on the inner side of the rolled leaf
- stomata are in pits
- spongy mesophyll is very dense
- store water in their stems
- stem is green for photosynthesis
- roots are wide set
- closing stomata when needed
- low water potential inside their leaf
- long tap root
49
Examples of xerophytes
- marram grass
- cacti
50
What is translocation
Mass flow of sucrose in the phloem from the source to the sink
51
What is a source in transpiration
Part of the plant that loads assimilates into the phloem sieve tubes
52
What is a sink in transpiration
A part of the plant that removes assimilates from the phloem sieve tubes
53
What type of process loads sucrose into the sieve tube
Active loading/process
- involves the use of energy from ATP in the companion cells
54
What is the energy in active loading used for
Actively transport hydrogen ions out of the companion cells
55
What is Co transport
Coupled movement of substances across a cell membrane via a carrier protein
- combination of facilitated diffusion and active transport
56
What is caused by sucrose moving into the phloem
Hydrostatic pressure
57
What does hydrostatic pressure cause
Pressure gradient
58
What happens at the source of transpiration
- sucrose enters the phloem
- lowers the water potential gradient
- water enters the phloem
- causes sap to move down the phloem
59
What happens at the sink in transpiration
- sucrose leave the phloem
- increases the water potential
- water leaves the phloem
