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Semester 2 Exams > APS 119: Plant physiology > Flashcards

APS 119: Plant physiology Flashcards

1
Q

define adaptation

A

heritable changes in genes that occurs through natural selectionn

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2
Q

define acclimation

A

changes in gene expression and metabolism - reversible and non heritable

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3
Q

what percentage of a plant is qater?

A

95%

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4
Q

what are four uses of water in a plant?

A

turgidity
photosynthetic processes
transpiration
translocation

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5
Q

what percentage of global rainfall is accounted for by transpiration?

A

40%

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6
Q

a single mature oak can transpire _______ liters per year. An acre of corn can transpire ______ per day

A

150,000 per year

15,000 per day

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7
Q

transpiration is u______

A

unidirectional

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8
Q

xylem transports _______ from _____ to _____-

A

water
root
shoot

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9
Q

phloem transports _____. from S____ to S____

A

solute

source to sink

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10
Q

if you look at a plant vasculature the xylem forms and _____ surronded by _______

A

cross shape surronded by phloem

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11
Q

in monocot plants phloem and xylem are found throughout the stem. where as because of the need to store ______ dicot plants have their vasculature concentrated to the _____

A

lignin

outside

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12
Q

when will root hairs form?

A

when there is little water avaliable

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13
Q

what are the four layers of the root?

A

epidermis - strong supporting cell layer - allows growth through soil
coretx - provides structure
endodermis - single layer of cells regulates water intake
pericycle - root development - stem cells of the root

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14
Q

two routes into the xylem

A

symplastic route - through cytoplasm - must go through membranes

apoplastic route - though the cell walls

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15
Q

what is the function of the casparian strip?

A

in the endodermis

  • cell membranes used to remove heavy metals - act as a filter
  • casparian strip forces water into the symplastic route and hence enables removal of heavy metals
  • prevents uncontrolled movement of water
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16
Q

how many types of aqua porins do humans have and arabidopsis

A

humans - 4

arabidopsis - 35

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17
Q

when is water loss heighest

A

photosynthesising, warm dry and windy conditions

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18
Q

describe cohesion tension theory

A

water molecules stick together by hydrogen bonding
forms a continuous column
loss from leaves pulls water up from xylem

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19
Q

where are boreal forests found?

A

a circumpolar belt northen hemisphere above 50 degrees north.

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20
Q

describe what happens when water freezes in the xylem of trees

A

dissolved gases form bubbles and are squeezed out
repeated freeze thawing creates larger bubbles
disrupts hydrogen bonding causes an embolism/ cavitation

water is no longer pulled up the xylem

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21
Q

how do trees tackle the problem of embolisms in freezing environments?

A

very narrow xylem - less vulnerable to embolism but means the tree grows slower

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22
Q

how did trees response to freezing evolve?

A

linked to drought tolerance
druier further north
focring water out of very dry soil can lead to bubbles
- gives the trees the gnetic toolbox to deal with the same problem of embolisms when freezing

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23
Q

photosynthesis is the basis for ____% of life on earth

A

99

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24
Q

how much CO2 is taken in by plants per year, and what is the anthropogenic emission value?

A

120Gt from plants

9Gt from anthropogenic emissions

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25
Q

when did photosynthesis evolve? what was different about this phptpsynthesis?

A
  1. 8 billion years ago

- used other molecules than water

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26
Q

three lines of evidence for when oxygenic photosynthesis arose

A

geology - red bands in rocks
fossil record
snowball earth

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27
Q

define stroma, thylakoids and grana

A 
stroma = space in chloroplast with a suitable pH for calvin cycle 
thylakoids = electron transport chain and ATP synthase 
grana = stack og thylakoids
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28
Q

describe the process of the light dependant reaction

A

light hits the light harvesting complex of PSII and hits the chlorophyll molecules - energy bounced and hits the reaction centre complex. reaction centre = P680

electron in reaction centre is excited. passed on to pheophytin

water is split to produce 2 for protons and 4 electrons (per two molecules of H2O) 4 photons needed for a molecule of oxygen

electron moves from phenophytin to plastoquione

then to cytochrome b6F

plastocyanin

PSI - P700 reaction complex takes electron from plastocyanin - reaction complex met
- light re excites electron and it is passed to gerredoxin

  • ferredoxin NADP reductase forms NADPH
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29
Q

which two proteins in the etc pump protons into the thylakoid lumen

A

plastoquinone and cytochrome b6F

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30
Q

how does cyclic electron transport work?

A

electron passed though PSI
ferrodixin passes electron back to cytochrome b6F
- no NADPH produced but ATP is produced

mutants that dont do cyclic electron transport dont do as well as those that do

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31
Q

for 2 H2O you recieve how many NADPH and ATP

A

4 ATP and 2 NADPH

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32
Q

what is an alternative na,me for the calvin cycle

A

calvin benson bassham cycle

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33
Q

what is the key enzyme envolved in the light independant reaction of photosynthesis?

A

RuBisCo

- adds CO2 to a C5 sugar

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34
Q

what are the three key processes of the calvin cycle

A

CO2 fixtation
reduction of organic molecule
regeneration of ribulose bisphosphate

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35
Q

describe the calcin cycle

A

RuBisco adds CO2 to ribulose 1,5 - bisphosphate. makes two lots of 3-phosphoglycerate

phosphate added to make 1,3-bisphosphoglycerate, uses one ATP. NADPH used to remove a phosphate making glyceraldehyde 3 -phosphate

glyceraldehyde 3 -phosphate is transformed into ribulose 5 - phosphate. need 5 glyceraldehyde to make 3 ribulose 5- phosphate. final ATP to reform ribulose bisphosphate

3 atp and 2 nadph used per cycle and requires multiple cycles to generate its components

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36
Q

what is photorespiration?

A

RuBisCo is an oxygenase enzyme it fixes O2 onto 2 - phosphoglycloate as well as CO2
- this occurs 25% of the time in current oxygen concentrations

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37
Q

what are the products of photorespiration?

A

2 carbon molecule and 3 phosphoglycerate

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38
Q

what is the light compensation point?

A

plants do respiration - carbon is lost through respiration. the balance between carbon lostvia respiration and carbon gained by photosynthesis is the compensation point

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39
Q

give adaptations of the photosynthetic proces to very high light intensity

A

smaller, thicker leaves, less chlorophyll (paler). reduce amount of light absorbed - more PSII less light harvesting complexes

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40
Q

how does photosynthesis adapt in the shade

A

less PSII

more light harvesting complexes

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41
Q

what happens when the etc recieves to much light energy?

A

run out of reaction centres
chlorphylls have to much energy
damage the PSII

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42
Q

when may photoinhibition occur?

A

when under extreme conditions the PSII is damaged

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43
Q

what is the worst case scenario for dealing with extreme light intensity?

A

excitation energy is passed to oxygen which creates free radicals

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44
Q

give short term methods plants use to acclimate to excsess sunlight

A

disspiate excess energy as heat - non photochemical quenching
- stimulate the xanthophyll cycle

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45
Q

describe the xanothrophyll cycle

A

pigment molecules (xanthophyll)

  • vioaxanthin is changed to zeaxanthin in light stress
  • zeaxanthin is an antioxidant - protects lipid membranes and acts as a regulator of non photochemical quenching
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46
Q

what is a long term acclimation plants can do to high light intensity? what part of the plant can do this?

A

phenotypic plasticity

younger leaves

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47
Q

what is C4 an adaptation for?

A

avoiding photorespiration

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48
Q

name the intermediates between the product of photorespiration and the desired product of photosynthesis

A 
2 phosphoglycolate 
glycine 
serine 
glycerate 
3 - phosphoglycerate
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49
Q

where does the process of converting 2 phosphoglycolate into 3 - phosphoglycolate occur?

A

peroxisome and mitochondria
directly uses 1 ATP
produces CO2 AND NH3
- NH3 costly to remove from the cell

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50
Q

what is the yield loss in tonnes per year of UK wheat from photorespiration?

A

3 million tonnes

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51
Q

what three factors effect how a species will differ in its response to photorespiration

A

oxygen and carbon dioxide concentrationn
rubisco structure
environmental factors

52
Q

what conditions favour photosynthesis over photorespiration

A

high CO2 concentration

low temperture (high temperture reduces RuBisCo specificity to CO2)

higher water levels - stomata dont need to be closed hence gases dont accumulate

53
Q

why did inputting the RuBisCo from red alage (more efficient) not increase the plants efficeincy?

A

because trade off between rate and specificity

54
Q

what are the four types of method to increse CO2 concentrations within plants

A

dissolved inorganic pump

C2

C4

CAM

55
Q

describe the dissolved inorganic pump method of carbon concentration

A

carbon dioxide turned into carbonate ions

pumled into pyrenoid - carbnonate reverted back into CO2 in pyrenoid

56
Q

describe C2 photosynthesis

A

40 angiosperm species

CO2 from photorespiration and shuttles back to rubsico (via a glycine pathway)

no additional ATP needed

57
Q

C4 photosynthesis occurs in ___ of plants but equates to ____% of primary productivity

A

3

25

58
Q

C4 photosynthesis concentrates carbon around rubsico by ____ times

A

3-10 times

59
Q

give the 7 steps of the C4 pathway

A

CO2 outside the leaf diffuses into mesophyll cells

converted into bicarbonate ions

then oxaloacetate

then moves to chloroplast and becomes malate moves to bundle sheath to form pyruvate and CO2

CO2 goes into the calvin cycle

pyruvate is shuttled back into the chlorophyll forms phosphenopyruvate which is added to bicarbonate ions to form oxaloacetate

60
Q

when is C3 photosynthesis better than C4? which means the % of C4 plants gets ______ nearer the equator

A

at lower temps - below 30 degrees

greater

61
Q

the water us per one gram of dry matter is about _____ in C4 compared to C3

A

double

62
Q

when did evolution of C4 photosynthesis occur

- monocts and dicots

A

21-35mya in monocots

15-21 mya in dicots

63
Q

how many times has C4 evolved?

A

62 seperate times

64
Q

for what percentage of the population is rice their staple grain?

A

50%

65
Q

because genetic enginerring of crop plants is illegal how is C4 inputted into plants?

A

mutagenesis - bombard crops with radiation until the desired effect is produced

66
Q

what is needed in a plant in order to implement C4

A

more bundle sheaths

vascular bundles closer together (reduce distancce CO2 must diffuse)

67
Q

CAM photosynthesis is an adaptation to________

A

low water conditions

68
Q

where is a supprising location where you might find CAm photosynthesis?

A

rainforest - in epiphytes - no rooting systems, high in canopy because of high tempertures water concentrationo is very low

69
Q

a lack of water means ______ photo respiration

A

more

70
Q

how can you tell by touching a plant wether or not it is CAM

A

CAM plants are more succulenct - more squishy

71
Q

CAM covers ___% of angiosperms

A

7%

72
Q

C4 works as a _____ seperation method, CAM is a ______ seperation

A

spatial

temporal

73
Q

describe how CAM photosynthesis works

A 
NIGHT 
stomata  open and CO2 moves into the cell 
converted into bicarbonate ionns 
convert a C3 into a C4 acid, via PeP carboxylase 
c4 acid (malate) moved to vacuole

DAY
malate leaves vacuole and is converted into C3 by losing a CO2

74
Q

is CAM more or less efficient than C4?

A

less

75
Q

give 3 examples of facultative CAM plants

A

ice plant
surinam purslane
clusia minor

76
Q

CAM may occur in plants that face conditions that mimic low water levels e.g.

A

salt stress
high light
long days
nitrogen and phosphate deficiency

77
Q

why is CAM advantegous in aquatic plants?

A

CO2 diffusion is 10,000 times slower

78
Q

_____ litres of air are required for ___ of sucrose

A

5000 litres of air for 1 gram

79
Q

CAM is ____ more efficient in water use than C3 and C4. C4 is _____ as efficient as C3

A

10 times

twice

80
Q

why does CAM conserve water?

A

at night time when the stomata are open the potential difference between water potential in the plant and the outside is much smaller than that at mid day

81
Q

whole plant adaptations to low water conditons

A

succulence - fill leaves with water
reduced leaves - absorb enought light through stems
compact growth form - reduce surface area compared to volume

ribs - notable on cacti, areas of tissue between them that can swell up

thick cuticle - stops transpiration

surface roots - run straight out over the surface to get as much water as possible

82
Q

leaf adaptations to low water conditons

A

thicker cutucle on leaves
regulate stomata opening
increase boundary layer e.g with leag hairs, spines, sunken stomata, sit in pits, rolled leaves

83
Q

describe how stomata open

A

plant forces protons out of the guard cells

leads to K+ uptake in guard cells reducing water potential

diffusion occurs into the guard cells

develops a pore 5-10ym thick

84
Q

CAM plants switch off their recptiveness to ______ because it can trigger the _______ to open

A

light

stomata

85
Q

what plant hormone controls water loss prevention?

A

Abscisic acid

86
Q

what are the three macro nutrients plalnts need?

A

Nitrogen
phosphorus
potassium

87
Q

chlorotic leaves

A

yellow leaves due to lack of nitrogen and hence amino acids

88
Q

three ways of getting biologically accsessible nitrogen

A

industry - hraber bosch processor N2+3H2—>2NH3

biologically - symbiosis
- reuction of nitrate to ammonia

lightening

89
Q

the harber bosch process uses ____ % of global energy

A

1-2%

90
Q

_tonnes of oil is needed for every ___ tonnes of fertiliser

A

2

1

91
Q

equation for conversion of nitrogen into ammonia

A

N2 + 8H+ + 8e- —-> 2NH3 + H2

92
Q

what are the three problems with the conversion of N2 into biologically accsessible forms of nitrogen?

A

sensitive to oxygen
very large input of enrgy in form of ATP
side reactions of hydrogen that needs to be removed

93
Q

how is it that legumes can be used as a cover crop ?

A

leguems have high concentrations of symbiotic bacteria which can convert N2 into accsessible forms of N

94
Q

desccribe the formation of a root nodule

A

rhizobia bacteria form an infection thread - invaginate the plasma membrane

enter root hair

form a bacteroid

root cells grow around the bacteroid to form a nodule

nodule develops vascular tissue

95
Q

in legumes a _____ of all carbon fixed goes to root nodules

A

third

96
Q

in low nitrogen environments two other methods of obtaining nitrogen can occur

A

parasitism

carnivours - from dead animals

97
Q

plants can tolerate _____ yg per meter squared for one hour but only __yg per meter squared as a yearly average

A

10,000

75

98
Q

nitrogen is involved in the G_____ S_____ C_____

A

glutamate synthase cycle

  • ammonia used to make glutamate and glutamine
  • from here every other amino acid can be formed
99
Q

what is phosphorus used for in plants?

A

nucleic acids, metabolties, phospholipids and ATP

100
Q

describe four steps on the phosphorous cycle

A

agriculture puts phosphate into the soil
leaches inot sea
falls into sediment
tectonic actovoty returns in to rocks

101
Q

what are two solutions to the impending phosphorus shortage?

A

apply more efficiently - 80-90% currently unavaliable

recycling

102
Q

describe how cluster roots tackle low phosphprus

A

proliferation of root growth
massive increase in root surface area produces high levels of citric acid
citric acid binds to metals in the surronding soil
releases attached phosphates from metals

103
Q

how do proteoid roots improve phosphate efficeincy?

A

no phospholipid bilayer
use galacto lipids
also lower protein production since young leaves dont photosynthesise
very few ribosomes

104
Q

potassium makes up ____ of a plants dry weight

A

0.5 -2%

105
Q

what is potassium used for?

A

opening stomata, transport of molecules

protein synthesis

106
Q

what form does potassium come in fertilisers

A

KCl

107
Q

why are specific transporters needed for potassium

A

same chemical group as Na+

Na+ is toxic in larger quantities hence cannot be allowed in as much as K+

108
Q

potassium can work as a oest control e.g. ______

A

fungal, bacterial and viral diseases
insects and nematodes
reduces all by up to 70%

109
Q

plant diseases are resposnsible for _____ of crop loss

A

70%

110
Q

iron

A

chlorophyll biosynthesis

111
Q

molybdenum

A

nitrogen absorbtion

112
Q

Nickel

A

nitrogen metabolism

113
Q

copper

A

chlorophyll and cell walls

114
Q

zinc

A

enzymes and transcription

115
Q

manganese

A

chlorophyll membranes

116
Q

born

A

cellular functions

117
Q

describe the structure of the phloem

A

continuous tubes of living cells
companion cells
sieve tube elements joined by sieve tube plates

118
Q

mass flow hypothesis

A

sugars loaded through phloem parenchyma by source (passive)

flow into phloem
high concnetrration in phloem brings in water from the xylem via osmosis

mass flow occurs towards the sink organs

sugars leave the phloem where they are needed

119
Q

what is the sugar transporter in arabidopsis

A

SUT1

120
Q

what is transported in the phloem?

A 
sugar#
amion acid 
organic acid 
protein 
potassium 
mRNA 
no aba or nitrate - must movev in xylem
121
Q

gove examples of plants that ahve C3 C4 and CAM

A

C3 Wheat, rice,
potatoes

C4 Maize, millet,
sugarcane

CAM Agave, vanilla,
pineapple

122
Q

what is the first product of photosynthesis in CAM C4 and C3

A

CAM and C4 = malate

C3 = glycerate

123
Q

describe the anatomy of the three types of photosynthesis

A

C4 - kranz anantomy

CAM - tissue succulence

124
Q

compare photorespiration in C3 to that of CAM and C4

A

40% in C3 (up to)

undectable in CAM and C4

125
Q

what is the CO2 compenstation point in C3 C4 and CAM

A

C3 - 40 ppm
C4 less than 5 ppm
CAM less than 5 ppm

126
Q

compare growth rates of C3 C4 and CAM

A

C3 - 5-20 g per meter squared per day
c4 50-60 g per meter squared per day
CAM 0.5 g per meter squared per day

Semester 2 Exams (10 decks)

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