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OCR Biology A > 3.1.3 - Transport in Plants > Flashcards

3.1.3 - Transport in Plants Flashcards

1
Q

What distinguishes stems from other parts of the plants

A

Presence of nodes and internodes

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2
Q

Role of vascular cambium

A

Responsible for secondary growth and contains meristematic tissue

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3
Q

Functions of roots

A

Anchor the plant in the ground
Store excess carbs
Absorbs water and minerals

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4
Q

Role of parenchyma

A

Involved in respiration, photosynthesis, storage and secretion
Heavily lignified

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5
Q

What is collenchyna tissue made of

A

Collenchyma cells
Pectin
Cellulose

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6
Q

Role of collenchyma

A

Provide support

Expands as the stem grows

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7
Q

Role of endodermal cells

A

Regulates the substances that enter

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8
Q

What is pericycle made of

A

Parenchyma and sclerenchyma

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9
Q

Role of pericycle

A

Maintains meristematic activity

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10
Q

What is xylem tissue made of

A

Tracheids
Vessel elements
Parenchyma
Sclerenchyma

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11
Q

Embolisms

A

Air bubbles formed in plant capillaries

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12
Q

Ions needed by plants

A 
NO3 ^2-
Mg ^2+
PO4 ^3-
K ^+
SO4 ^2-
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13
Q

What is the cortex made of

A

Parenchyma

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14
Q

Transpiration

A

Loss of water from leaves of a plant, occurs from underside of leaf (stomata)
Water moves from areas of high hydrostatic pressure to areas of low hydrostatic pressure

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15
Q

Functions of water in plants

A

Turgidity - keep stems and leaves rigid
Photosynthesis
Enzyme reactions - metabolic processes occur in solution
Transport - ions absorbed in solution and transported in xylem

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16
Q

Apoplastic pathway

A

Water moving from soil solution to root hair and across cortex to the xylem in the cell walls

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17
Q

Symplastic pathway

A

Water moving from soil solution to root hair and across cortex to the xylem through the cytoplasm and plasmodesmata

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18
Q

Vacuolar pathway

A

Water moving from soil solution to root hair and across cortex to the xylem through the vacuoles

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19
Q

Factors affecting rate of transpiration

A

Temperature
Humidity
Light intensity
Wind

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20
Q

Lignin

A

Causes spirals in xylem

Allows cells to stretch/expand

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21
Q

Adaptations of vessel elements

A

Hollow lumen
Perforated cell ends
Lignin for rigidity

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22
Q

Casparian strip

A

Controls amount of water coming in the endodermis

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23
Q

Factors affecting transpiration

A 
Temperature 
Humidity 
Light intensity 
Air movement 
Soil water availability
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24
Q

Control variables when using potometer

A

Cut at an angle to increase SA of lumen
Bung to stop water evaporating
Assemble potometer underwater - prevents air from entering
Dry leaves - no water molecules blocking stomata

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25
Functions of roots
Anchor the plant in the ground Store excess carb reserves Absorb water and minerals
26
Purpose of root hairs
Provide a very large surface area for uptake of water and ions
27
Why is the root tip covered by a cap of cells
Protects dividing cells of the top and lubricates root movement
28
Meristem in roots
Increase height of plants
29
Meristem in stem
Increase plant girth
30
Stele
Section in middle of transverse section of dicotyledonous root Endodermis Xylem tissue Phloem tissue
31
Water uptake
Water enters capillaries from soil (osmosis) Apoplast and symplast pathways (root hair cells to cortex) Water leaves apoplast at endodermis and enter from symplast Water enters xylem under root pressure then travels in tracheids and vessel elements Water carried to mesophyll through small veins Evaporates in leaf air spaces and from stomata
32
Pith
Made of parenchyma cells | Forms inner cortex
33
Epidermis in plants
Protects moist under tissues from desiccation and invasion of pathogens
34
Transpiration
Loss of water from a plant | H2O moves from an area of high hydrostatic pressure to areas of low
35
What is transpiration affected by
Gravity Electrostatic forces Water potential
36
How does water enter the xylem from the soil
H2O moves into cell as active transport transports inorganic ions into the cell (ATP) Lowers H2O potential --> higher conc. of solute; conc. gradient H2O can moves from an area of high WP (soil) to an area of low WP (cell) - osmosis
37
Translocation
Movement of dissolved solutes (sucrose) from sources to sinks through the phloem
38
Why is translocation bidirectional
Roots can act as a sink by releasing carbs and also as a store depending on time of year
39
Process of translocation
Glucose formed in photosynthesis and condensed (sucrose) Moves into companion cell by active transport (active loading) Reduces WP allowing H2O to move in (osmosis) Creates high hydrostatic pressure - mass flow Sucrose diffuses out of phloem to where it's needed for growth and storage
40
Mass flow
Assimilates enter sieve tube and lower wp Water enters through osmosis and increases hydrostatic pressure Assimilates leave at sink and increase wp Water leaves and lowers hydrostatic pressure High hydrostatic pressure, forcing sap through vessels towards regions of lower pressure
41
How does the process of translocation reoccur
Sink removes sugar, increases WP --> H2O leaves tubes (osmosis) keeping hydrostatic pressure low
42
Tonoplast
Membrane around cell wall
43
Function of endodermis
Controls amount of H2O coming in (casparian strip)
44
What is the Caspian strip made of
Suberin - impermeable to water, lipid
45
What does Casparian strip stop
Movement of water through the apoplast
46
Source to sink
Sugar moving from where its made to where its stored
47
Possible sinks
Seeds Fruit Meristems Roots
48
Possible sources
Leaves Food stores in seeds when they geminate Storage organs
49
How does water get up the xylem
Root pressure Capillary action Transpirational pull H2O cannot return to cortex through apoplast therefore pressure builds up in cortex pushing H2O up xylem
50
Root pressure
Endodermis in roots uses metabolic energy to pump ions into root Reduces WP in xylem and medulla H2O moves across endodermis into medulla (osmosis)
51
Capillary action
H2O can rise up a narrow tube against the force of gravity
52
Cohesion
Water molecules sticking together
53
Adhesion
Attraction between water molecules and the walls of the xylem
54
Transpirational pull
Loss of H20 through leaves must be replaced by H2O in xylem H2O moves up xylem as a result of tension, created by loss of water in leaves As H2O moves out of xylem, the whole column gets drawn up due to cohesion
55
How does water move in and exit the leaf
Enters through the xylem, passes through mesophyll (osmosis) and diffuses through air space in spongy mesophyll As H2O vapour collects WP rises, when higher in the leaf --> diffuses out of stomata
56
Mesophytes
Plants adapted to a habitat with adequate water
57
Halophytes
Plants adapted to a salty habitat
58
Xerophytes
Plants adapted to dry habitats
59
Adaptations of xerophytes
Rolled leaves - reduce SA Reduced no. and size of stomata - reduces diffusion Sunken stomata - creates pocket of water vapour Thick waxy cuticle - impermeable Hairy leaves - traps water vapour Dense spongy mesophyll - smaller surface area for evaporation Thick stem - stores water
60
Hydrophytes
Plants adapted to live in freshwater
61
Adaptations of hydrophytes
Aerenchyma - parenchyma with many air spaces (buoyancy and flotation): allows O2 to diffuse to roots for aerobic respiration Reduced root system - water can diffuse directly into leaves, feathery roots hold up plant Large thin leaves Stomata on the upper surface only
62
Adaptations of xylem
End walls removed to form long tubes No cytoplasm/cell organelles - little resistance of flow of water Lignified (waterproofing and strengthening) Bordered pits - allow movement of water between vessels
63
Adaptations of sieve tube elements
``` Form long tubes End walls are retained End walls contain many sieve pores (sieve plates) Thin layer of cytoplasm Very few organelles; no nucleus ```
64
Adaptations of companion cells
Closely associated with sieve tube elements Connected to sieve tube elements by many plasmodesmata Dense cytoplasm with many mitochondria Large nucleus
65
Cohesion-Tension theory
Evaporation at top of the xylem creates tension in the xylem | Water molecules are cohesive and form a column which is then pulled up by tension
66
Transpiration stream
Movement of water up xylem vessels from roots to leaves (area of high hydrostatic pressure to area of low hydrostatic pressure)
67
Translocation occurs through the sieve elements by ...
Mass flow
68
What gets transported in translocation
Assimilates such as sucrose and amino acids
69
Why is using potometer not accurate
Assumption that water uptake by plants is the same as water loss BUT water is used photosynthesis and is produced in respiration
70
Why does wind affect transpiration
Vapour around stomata is blown away Reduces water vapour around stomata Creates steeper wpg
71
Active loading
H+ ions pumped out of cc using active transport Uses conc. gradient to move back into cc w. sucrose through a cotransporter protein Sucrose builds up and diffuses through plasmodesmata into sieve tubes Reduces wp
72
Why is water loss from the leaves unavoidable
Stomata opens for gas exchange for photosynthesis Photosynthesis is necessary to make sugars Water lost through the cuticle
73
Why is sucrose transported in translocation and not glucose
Soluble so can easily travel in solution | Metabolically inactive so not used during transport
74
Why does low temperature cause death of cells
Ice forms and pierces membranes | Denaturing of proteins
75
Evidence for the role of active transport in root pressure
Some poisons affect mitochondria and prevent production of ATP, when cyanide is applied to root cells, root pressure disappears Root pressure increases w a rise in temp and decreases w/ a fall in temp --> chem reactions If O2 levels fall or respiratory substrates so does root pressure Guttation
76
Evidence for cohesion tension theory
Changes in diameter of trees - when transpiration is at its highest as is the tension, diameter shrinks When a xylem vessel is broken air is drawn in rather than water leaking out Plant can no longer move water up the stem as continuous stream is broken
77
Evidence for translocation
Microscopy allows us to see he adaptations of cc for active transport If mitochondria of cc are poisoned, translocation stops Flow of sugars n phloem is 10,000x faster than diffusion ---> active process Aphids
78
Why is water stopped from entering the apoplast through the casparian strip
Ensures that water and dissolved mineral ions (especially nitrates) have to pass into the cell through the plasma membrane so the water and ions are in the cytoplasm Prevents water from cortex going back to medulla

OCR Biology A (25 decks)

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