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Biology > 2.3 plant transport > Flashcards

2.3 plant transport Flashcards

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1
Q

what does photosynthesis produce

A

glucose through sunlight

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2
Q

atp ?

A

energy required to move and transport substances

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3
Q

2 types of vascular tissue

A

xylem and phloem

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4
Q

what is the xylem

A

tissue in plants that move water and dissolved substances upwards

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5
Q

what is the phloem

A

plant tissues containing sieve tube elements and companion cells, translocating sucrose and amino acids from the leaves to the rest of the plant

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6
Q

how are plant roots adapted for the uptake of water

A

give a large surface area for the absorption of water by osmosis

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7
Q

where is the vascular bundle in relation to the plant

A

the stem

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8
Q

types of tissue (plant)

A

parenchyma
collenchyma
sclerenchyma

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9
Q

what is the parenchyma

A

‘packing’ tissue where cells are not specialised, they are alive with thin walls.

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10
Q

where is parenchyma found

A

in the cortex

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11
Q

what is the collenchyma

A

modified parenchyma cells, still alive but have irregular shaped thicker cellulose walls
supportive tissue

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12
Q

where is collenchyma found

A

cortex

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13
Q

what is the sclerenchyma

A

deads cells (have no cell contents. often stained red, have very thick secondary cell walls which have been lignified

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14
Q

where is sclerenchyma found

A

in our vascular bundles

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15
Q

absorption of water by the root

A

when roots make contact with the soil, water moves into the roots via osmosis

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16
Q

where are water and mineral ions found

A

in the soil

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17
Q

why does water need to get to the xylem

A

to be distributed around the plant

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18
Q

what are the 3 ways water moves through the root cells and into the xylem tube

A
  • apoplast pathway
  • symplast pathway
    -vacuolar pathway
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19
Q

what is the pathway of choice for water

A

apoplast

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20
Q

explain the apoplast pathway

A

fastest pathway
water moves through cell walls
stops when it hits the endodermis

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21
Q

explain the symplastic pathway

A

moves through cytoplasm and changes cells through the plasmodesmata

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22
Q

explain the vacuolar pathway

A

water moves through the vacuoles

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23
Q

what can water not pass through

A

the impermeable waterproof barrier in the cell wall

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24
Q

what is the endodermis

A

a single layer of cells around the pericycle and vascular tissue of the root

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25
Q

what does the casparian strip do

A

stops the flow in the apoplast pathway

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26
Q

what is the casparian strip do

A

impermeable band of suberin in the cell walls of endodermal cells, blocking the movement of water in the apoplast pathway forcing it to go into the cytoplasm (symplast pathway)

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27
Q

why is the casparian strip important

A

because water can only enter the xylem from the symplast or vacuolar pathway

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28
Q

explain how water entering the xylem in the root

A

this cannot happen from the apoplast pathway because the lignin walls are waterproof. water enters xylem via the symplast or vacuolar pathway

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29
Q

what are the 2 transport systems
(water)

A
  • transpiration
    -translocation
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30
Q

what is transpiration

A

movement of water molecules and dissolved mineral ions

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31
Q

where does transpiration happen

A

in the xylem vessels

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32
Q

does transpiration require energy

A

no its a passive process

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33
Q

what is translocation

A

the movement of sugars (sucrose) and amino acids

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34
Q

where does translocation happen

A

in phloem vessels
sieve and companion cells

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35
Q

does translocation require energy

A

yes it is an active process

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36
Q

what colour do xylem vessels stain
why?

A

stain red
because they’re dead

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37
Q

explain the process of xylem vessels

A
  • early on in life each xylem vessel is separate from eachother
  • as it matures it dies and the end cell walls break down (forms a long tube of cells)
  • the long tube can run all the way up the stem from the roots to the leaves
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38
Q

what is the tube of xylem vessels made of

A

cellulose

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39
Q

what happens as a result of cellulose not being strong enough

A

it is strengthened through the addition of lignin making the walls strong

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40
Q

what does lignin appear as

A

rings/spirals

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41
Q

what are the 2 functions of xylem

A

1) transport of water and dissolved mineral ions
2) providing mechanical strength and support

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42
Q

explain how xylem tissue is formed

A

xylem parenchyma (is living) it modifies and turns to xylem tissue which is dead

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43
Q

what is xylem tissue made up of

A

tracheids and xylem cessles

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44
Q

explain tracheids

A

walls made from lignin (hard, strong and waterproof) cells can elongate, have tapered endss
the walls have gaps
spindle shapes

45
Q

what are the gaps in tracheids called

A

pits

46
Q

role of pits in tracheids

A

where water moves through

47
Q

where are xylem vessels found

A

in angiosperms only

48
Q

explain xylem vessels

A

they are really well adapted
water goes straight up

49
Q

tracheids vs vessels

A

water travelling straight up the plant in vessels is so much more efficient than the twisting path through tracheids that angiosperm have become the dominant plant type on earth

50
Q

2 explanations for water to move from the root endodermis to the xylem

A

1- an increased hydrostatic pressure in root endodermal cells pushes water into the xylem
2- the decreased water potential in the xylem (below the endodermal cells) draws water in by osmosis across the endodermal cell membrane

51
Q

how does water move into the xylem

A

by osmosis down a concentration gradient

52
Q

what does water coming into the xylem do

A

generates an upwards push, the root pressure on water already in the xylem

53
Q

explain the uptake of minerals

A

1) minerals absorbed into root hair by active transport
2) mineral ions can also move along the apoplastic pathway in solution

54
Q

what does the casperian strip do to mineral ions

A

prevents the movement in the cell wall so mineral ions enter the symplast pathway in the cytoplasm by AT and are diffused or actively transported into the xylem

55
Q

what does AT allow
(mineral ions)

A

the plant to absorb ions at the endodermis

56
Q

explain the movement of water from root to leaf

A

water moves down a water potential gradient, air has a very low water potential and soil water has a very high water potential so water moves from roots to leaves in the xylem

57
Q

3 mechanisms of the movement of water from root to leaf

A

1) cohesion tension theory (transpiration)
2) capillarity
3) push of water up the xylem (root pressure)

58
Q

explain cohesion tension theory/ transpiration

A

evaporation of water into the atmosphere from the stomata of the plants creates a pulling force drawing the water column up the xylem (tension) the water molecules are strongly attracted to eachother (cohesion)

59
Q

explain adhesion

A

occurs as a result of attraction between the charges of the water molecules and the hydrophillic lining of the vessels
adhesion holds the column of water in place and contributes to water movement

60
Q

explain capillarity

A

movement of water of narrow tubes by capillary action, only operates over short distances, up to a meter. only makes a small contribution to water movement in plants more than a few CM high

61
Q

capillarity
HOW?

A

cohesion between water molecules generates surface tension which combines with water’s attraction to the xylem walls draws the water up

62
Q

explain root pressure

A

upward force on water in roots, derived from osmotic movement of water into the root xylem.
in the root, endodermis cells actively transport minerals ions into the xylem, reducing its water potential

63
Q

summary of root pressure

A
  • water is drawn in
  • hydrostatic pressure increases
  • water is pushed upwards
64
Q

what is the site of transpiration

A

stomata

65
Q

what is transpiration

A

the loss of water by evaporation, which is water vapour from leaves and shoots of plants. this causes the transpiration stream

66
Q

what is the transpiration stream

A

continual flow of water in at the roots, up the stem to the leaves and out to the atmosphere

67
Q

what does the rate of transpiration depend on
these factors interact with eachother

A

1- genetic factors: genes controlling the number, distribution and size of stomata
2- x4 genetic factors: temperature, humidity, air movement. these x3 affect the water potential gradient between water vapour in the leaf and the atmosphere
and light, by controlling the degree of stomatal opening

68
Q

harmful aspect of transpiration

A

water loss

69
Q

useful aspects of transpiration

A

water uptake (photosynthesis)
water distribution (turgidity)
ion distribution and evaporative cooling

70
Q

what is humidity

A

a measure of number of water molecules in the air. the air inside a leaf is saturated with water vapour, so it’s relative humidity is 100%

71
Q

what is still air

A

accumilation of water around the stomata

72
Q

what does still air do

A

reduces water potential gradient

73
Q

how do we measure the rate of transpiration

A

using a potometer, this actually measure the rate of water absorption, but this should the same as the rate of transpiration

74
Q

what do you need to do to set up a potometer correctly

A

cut the shoot under water (prevent air bubbles forming in the xylem)
keep the leaves dry
set up apparatus under water
ensure all joints are airtight

75
Q

what does the reservoir do
specified prac

A

returns the bubble to zero/starting point

76
Q

what does the air bubble show
specified prac

A

movement of the bubble indicates the volume of water taken up by the shoot

77
Q

rate of water uptake =

A

speed of movement of air bubbles x cross-sectional area of capillary tube

78
Q

3 groups of plants classified according to their adaptations to water ability

A

mesophytes
hydrophytes
xerophytes

79
Q

describe mesophytes conditions

A

live in habitats with adequate water supply

80
Q

what adaptations do mesophytes have

A

close stomata in the night to decrease water loss
shed their leaves in the winter to survive unfavourable times (frost)
bulbs to survive winter

81
Q

xerophytes conditions

A

live in conditions where water is scarce

82
Q

explain xerophytes

A

highly specialised, the water lost via transpiration is greater than water taken up by roots

83
Q

example of a xerophyte

A

marram grass

84
Q

describe living conditions of hydrophytes

A

water plants, they grow submerged or partially submerged in water

85
Q

example of a hydrophyte

A

water lily

86
Q

adaptations of water lily

A

-no waxy cuticle because the plants are submerged in water so water loss isn’t a problem
- stomata are on the upper surface, the underside of the leaf is submerged. stomata must be on the upper leaf to allow gas exchange
-plant is surrounded by water, little need for highly developed transport tissues, xylem is poorly developed.
- stems and leaves have large air spaces (provides buoyancy to the plant tissue when submerged)
- water is a support medium, little or no lignified support tissues are needed

87
Q

adaptations of marram grass

A

-rolled leaves: large, thin walled epidermal cells at the bases of the grooves shrink when they lose water from excessive transpiration, causing the leaf to roll inwards, reduces transpiration
-reduced leaf area/ less area for evaporation
-hairs: stiff, interlocking hairs trap water vapour and reduces the water potential gradients
- thick waxy cuticle: a waxy covering which reduces water loss by evaporation from the epidermal tissue. No stomata, outer epidermis small thick-walled cells
- sunken stomata- stomata are found in the grooves on the inner side of the leaf, they allow water vapour to accumulate above the stomatal pore. increases the humidity which reduces the water potential gradient between the inside of the leaf and the air chamber. reduces the rate of transpiration

88
Q

what is translocation

A

the transport of soluble organic materials, sucrose and amino acids

89
Q

what and where is transported in the phloem

A

products of photosynthesis, away from the site of synthesis in the leaves to all other parts of the plant

90
Q

what is the source

A

leaves

91
Q

what are the products of photosynthesis used for

A

growth and stroage

92
Q

why is sugar transported as sucrose and not glucose

A

because it is less reactive than glucose is

93
Q

4 types of tissue cells in the phloem

A

companian
sieve tubes
phloem fibres
phloem parenchyma

94
Q

explain the structure of phloem

A

contains sieve elements which end in sieve plates, these plates contain pores through which cytoplasmic filaments extend linking cells. not other organelles are in the sieve elements. companion cells contain mant mitochondria which release ATP
they also contain organelles for protein synthesis.

95
Q

what does ATP help in the phloem

A

helps sucrose enter the sieve tube elements

96
Q

what are both sieve tube elements and companion cells

A

alive

97
Q

sieve tube elements

A

contain no nucleus and very little cytoplasm or organelles leaving room for mass flow of sap.

98
Q

how do sieve tube elements organise themselves

A

stack end to end and are separated by sieve plates.

99
Q

what do sieve plates allow

A

movement between sieve elements

100
Q

role of companion cells

A

carry out metabolic processes, make proteins and ATP for sieve tube elements

101
Q

how are companion cells connected to sieve tube elements

A

by plasmodesmata

102
Q

explain what ringing experiments have provided

A

evidence to support translocation in the phloem

103
Q

briefly describe what was found after this experiment

A

phloem was removed, analysis revealed that sucrose accumulated above the cut ring. provided evidence that sucrose was transported to this region of the stem by translocation.
there was also no sucrose below the ringed area. sucrose couldn’t be transported here as the phloem tissue had been removed

104
Q

evidence to support translocation in the phloem

A

aphids have a stylet, it is inserted directly to the sieve tube allowing the aphid to feed on the sugary sap, stylet is lasered off. analysis shows the sap contains products of photosynthesis- sucrose and amino acids

105
Q

explain radioactive labelling

A

technique showed sucrose is transported upward and downwards.

106
Q

what is the mass flow theory- what does it suggest

A

is the theory by which we think solute transport occurs in plants, from the source (highest conc.) to the sink (lowest conc)
suggests there is a PASSIVE MASS FLOW of sucrose

107
Q

summary of mass flow theory

A
  • initially high hydrostatic pressure in the source because dissolved sucrose reduces the water potential and draws water in by osmosis this increases the water potential
  • sucrose is pushed into the phloem, due to the high hydrostatic pressure. this increases the water pressure and reduces the water potential
    -water flows along the sieve tube element by osmosis from high to low hydrostatic pressure
  • sucrose is removed from the sieve tube by the surrounding cells at the sink and increases the water potential in the sieve tube
  • water moves out of the sieve tube and reduces the hydrostatic pressure- waters lost by osmos
108
Q

arguments against mass flow theory

A
  • rate of translocation is 10,000 times faster than it would be if substances were moving by diffusion
  • sieve plates with tiny pores act as a barrier impeding flow
  • sucrose and amino acids move at different rates and in different directions in the same in the same phloem tissue
    -phloem tissue has a high rate of oxygen consumption, and translocation is stopped when a respiratory poison such as cyanide enters the phloem
    -companion cells contain lots of mitochondria and produce ATP but the mass flow hypothesis fails to suggests a role for the companion cells

Biology (12 decks)

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