Transport in Plants Flashcards
(95 cards)
1
Q
What is the primary function of transport systems in organisms?
A
To exchange substances with external environments.
2
Q
Why do organisms need transport systems?
A
Metabolic demands, surface area to volume ratio, and size.
3
Q
What is a dicotyledonous seed?
A
A seed that has 2 cotyledons (seed leaves).
4
Q
What are herbaceous dicots?
A
Dicots with soft tissue and a short life cycle; they die back at the end of the growing season.
5
Q
What are arborescent dicots?
A
Dicots with hard tissue and a long life cycle; they can live for many seasons.
6
Q
What is the vascular system?
A
The transport system in plants.
7
Q
What is a vascular bundle?
A
The arrangement of transport systems in plants.
8
Q
What does xylem transport?
A
Fluids and minerals.
9
Q
In which direction does xylem transport substances?
A
Upwards, from roots to leaves.
10
Q
What does phloem transport?
A
Products of photosynthesis (sugars and amino acids).
11
Q
In which direction does phloem transport substances?
A
Upwards and downwards , from leaves to the plant.
12
Q
What is the midrib of a dicot leaf?
A
The main vein that carries vascular tissue around the organ and helps with leaf structure.
13
Q
Where is the vascular bundle located in roots?
A
In the middle, to help with the tugging of the plant.
14
Q
Where is the vascular bundle located in stems?
A
Around the edge, to provide strength and support.
15
Q
What happens to xylem when it matures?
A
It becomes dead as there is no cytoplasm and nucleus.
16
Q
How does xylem transport substances?
A
Through a passive process.
17
Q
What is the structure of xylem?
A
Spiral of lignin around the lumen, pits for water transfer, and gaps where cell walls have been lost.
18
Q
What are companion cells in phloem responsible for?
A
Keeping phloem alive.
19
Q
How are companion cells linked in phloem?
A
By plasmodesmata.
20
Q
What do sieve plates in phloem allow?
A
Solutions to pass through.
21
Q
What happens to phloem organelles as large pores appear?
A
They break down.
22
Q
What are sclerenchyma fibers?
A
Additional support found around the edge and inside vascular bundles.
23
Q
What is the role of parenchyma in vascular bundles?
A
It acts as packaging tissue, separates xylem and phloem, stores food, and contains fanning deposits.
24
Q
How does water help structure?(2)
A
-Provides a hydrostatic skeleton to support stems and leaves.
-Drives cell expansion- allows plant roots to
25
What adaptation do root hair cells have that increases their efficiency?(3)
-Large surface area to volume ratio on microscopic -hairs
-Microscopic size allows penetration through soil particles
-Thin surface layer to allow faster osmosis and diffusion
26
What maintains the water potential between soil water and root hair cells?
Concentration of solutes in the cytoplasm of root hair cells
27
What are the pathways of water transport in plants?
Apoplast pathway, Symplast pathway, Vacuolar pathway
28
Describe the Apoplast pathway.
Water moves along cellulose cell walls and intercellular spaces without resistance.It reaches the endodermis and is forced into the symplast pathway by the Casparian strip.
29
What is the Symplast pathway?
Water passes through the cytoplasm from cell to cell via plasmodesmata by osmosis down a water potential gradient
30
What is the Vacuolar pathway?
Water moves through the cell surface membrane into vacuoles and from vacuole to vacuole via plasmodesmata .It also leads to the endodermis and forces water into the symplast pathway.
31
Why are the Apoplast and Vacuolar pathways forced into the Symplast pathway?
To prevent toxic substancesfrom soil water from reaching living tissues.The membrane has no carriers to allow toxic substances through.
32
What evidence supports the role of active transport in root pressure?
Cyanide inhibits ATP production which will be introduced into root cells so there will be no root pressure
-It depends on rise and fall of temperature
33
What is the Casparian strip?
A waterproof layer of suberin which covers the endodermal cells
34
What is transpiration pull?
Water lost by evaporation by stomata which creates a suction force that drives water upwards resulting in tension in the xylem
35
What is the Cohesion-tension Theory?
As water is polar (contains hydrogen bonds ) the molecules adhere to walls of xylem and the cohesive force creates a continuous column of water.
36
What happens if the column of water in the xylem is broken?
Water can be transferred by pits
37
What evidence supports the Cohesion Theory?
-Trees shrink in diameter during high transpiration-day
-Air is drawn into the vessel and water is expelled when vessel is broken.
38
What creates root pressure in plants?
Water entering the stele creates a root pressure
39
How does water help metabolism in plants?
- loss of evaporation keeps plants cool
-raw material for photosynthesis
40
Transpiration Definition.
Loss of water vapour through the leaves and stem of the plant.
41
What is the transpiration stream?
Moves the water from the roots to the leaves via the xylem.
42
Describe the movement of water through the leaf.
-Stomata is open water vapour diffuses out of the pores into the outside down a water vapour potential gradient.
-water is replaced by water from spongey mesophyll
-water lost through leaf lowers water potential
-if water is not replaced then cells lose turgor and leaf may wilt
43
What is stomata?
The pores which allow exchange of substances.
44
What are guard cell features?(4)
-unevenly thick walls which helps them change shape
-ion pumps in plasma membrane
-has mitochondria
-chloroplasts
45
What happens when the stomata is open?
Water will be lost in transpiration
46
How does the stomata open?
increase in guard cell turgor- water available, low intercellular co2,high light intensity
47
What happens when the stomata is closed
-Roots send hormones to guard cells to trigger K+ levels to lower and water potential to rise.
-Water conserved
-water drown out by osmosis causes turgor loss
48
How does light intensity effect the rate of transpiration?
It increases rate. Stomata is open for gas exchange due to photosynthesis so increase water vapour loss.
49
How does the number of leaves on a plant effect the rate of transpiration?
More leaves, larger surface area for vapour loss.
50
How does the size, position and number of stomata effect the rate of transpiration?
Increases rate , many large stomata means more water vapour loss but slow vapour loss occurs when stomata is on underside of leaf
51
How does the presence of cuticle effect the rate of transpiration?
Reduces evaporation
52
How does relative humidity effect the rate of transpiration?
Reduces rate, smaller water vapour potential in leaf than outside.
53
How does temperature effect the rate of transpiration?
High temperature increases.
54
How does air movement effect the rate of transpiration?
Increases as air movement will carry away water vapour just diffused maintaining water potential.
55
How does soil water availability effect the rate of transpiration?
Less water in soil means less water can be replaced so water loss is reduced.
56
What is a potometer?
A device to estimate transpiration rates.
57
Why do you need to cut the leafy shoot under water?
Prevents air bubbles from being formed in the xylem and blocking flow of water
58
Why do you need to let the plant sit for 5 minutes before taking measurements?
To let the plant equilibrate to conditions.
59
Why do you need to put petroleum jelly on joints
To keep water tight and prevent the column of water breaking
60
Why do you need to keep the capillary tube horizontal?
To keep the air bubble from moving as its density relative to water.
61
What is translocation?
The movement of assimilates
62
What is assimilates?
Name given to products of photosynthesis that are transported by translocation
63
What is a source?
A Part of a plant where assimilates are made and released.
64
What is a sink?
A part of the plant where assimilates are transported to. For storage or respiraition
65
What are examples of sources in a plant?
-Green leaves and stem
-Storage organs like tubers and tap roots
-food stores in seeds when they germinate
66
What are examples of sinks in a plant?
-roots that are growing
-dividing meristems
67
Why is sucrose the main carbohydrate transported?
As it is not used in metabolism so it unlikely that it will be metabolised in transport process.
68
What is active loading?
69
What is mass flow?
Source -Sucrose loaded into phloem->reduces water potential
-water is also loaded into phloem by osmosis with increase hydrostatic pressure
-Water moves down ( moves from low hydrostatic pressure to low)
-sucrose removed from phloem increases water potential
Sink -water removed reduces hydrostatic pressure
70
What is the evidence for translocation?
-Advances in microscopy- see adaptations of companion cells
-if mitochondria is poisoned translocation stops
-translocation is 10,000 faster than diffusion-> suggests active transport
-Aphid studies-> inserts stylets into phloem and sap flows under pressure
71
What is a habitat?
A place where an organism lives
72
What is an adaptation?
A positive characteristic of an organism which has been favoured by natural selection
73
What is water potential?
A measure of tendency of water molecules to diffuse from one place to another.
74
What is a Mesophyte?
Able to take up sufficient water to replace transpiration. eg trees
75
What is hydrophytes?
Live either partially or completely submerged in water- problems with taking up oxygen. eg lily pads
76
What is Xerophytes?
Live in areas where water is lost via transpiration is greater than taken up by roots eg cacti
77
How does a thick way cuticle helps Xerophyte? examples?
It prevents water loss as the waxy layer covers the epidermis so that no water can escape through it. -cacti
78
How does reduced leaves helps a Xerophyte? example?
Reducing leaf area. The narrow leaves have reduced surface area to volume ratio which minimises water loss. -conifer needles, cactus spines
79
How does reduced number of stomata help a Xerophyte? example?
Reduces water loss and gas exchange capabilities. -
80
How does sunken stomata help a Xerophyte? example?
It creates a microclimate of still and increases humidity which reduces water potential gradient. - marram grass, couch
81
How does hairy leaves help a Xerophyte? example?
It creates a microclimate of still and humid air-> reduces water potential gradient. It also minimises surfaces. -marram grass, cacti
82
How does curled leaves help a Xerophyte?
It creates a microclimate of still and produces humid air which reduces water loss. - marram grass
83
How does succulents help Xerophytes ?
They produce water storage in specialised parenchyma tissue in the stems and roots- used for sunny droughts. - cacti, aloe Vera
84
How does leaf loss help Xerophytes?
The plant loses leaves when water is not available. They photosynthesize with less water.-Palo Verde
85
How does root adaptations helps Xerophytes?
-Long tap roots that can grow several meters which can acess water below surface
-Wide spread of roots with large surface area this absorbs water available
-marram grass, cacti
86
How does a very thin or no waxy cuticle help Hydrophytes?
They do not need to conserve water
87
How does wide flat leaves help Hydrophytes?
They are used to capture as much light as possible as they spread across the water surface.- water lilies
88
How does a high number of stomata help Hydrophytes?
It maximises gaseous exchange as stomata always open due to no turgor loss.
Need to be in contact with air.
- water Lilies
89
How does a reduces structure of plant help hydrophytes?
The water supports the leaves so there is not need for structure. rice, water lily
90
How does Aerenchyma helps hydrophytes?
Contains specialised parenchyma tissue in the leaves, stems and roots.
The tissue has many large air spaces which helps with transport for oxygen.
91
How does large surface area of stems and roots help Hydrophytes?
Maximises area for oxygen and photosynthesis
92
How does air sacs help Hydrophytes?
They help the plants float on the water
93
How does small roots help Hydrophytes?
The water diffuses directly into the stem and leaves
94
How does the casparian strip prevent ions from reaching the xylem?
The strip is waxy so not water can get through.
Forces water to pass through plasma.
The phospholipids repels the ions and charged particles.
95
What are the function of pits?
Lateral movement of water.
