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Lec 144 > Lecture 4-6 (plant Response To Pollution, Oxone Depleition And Co2) > Flashcards

Lecture 4-6 (plant Response To Pollution, Oxone Depleition And Co2) Flashcards

1
Q

How does “bad ozone” form? (Give forming components)

A

Bad ozone is a secondary pollutant formed from photochemical reactions of nitrogen and volatile organic compounds in the trophosphere

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2
Q

Where are good and bad ozone found?

A

Good ozone is found in the stratosphere, bad in the trophosphere

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3
Q

What does a 1% decrease in stratospheric ozone cause?

A

A 2% increase in UVB radiation reaching the biosphere

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4
Q

What is the wavelength of visible light?

A

380 to 700 nm

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5
Q

What is significant about the wavelength range 400-700 nm?

A

This is the wavelength range for photosynthetically active radiation, which is the range of light that photosynthetic organisms can use in photosynthesis

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6
Q

What percentage of total sunlight is par, and what percentage of this is caught by plants?

A

50% of sun is par, 2-10% is captured by plants

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7
Q

What is the wavelength for uv radiation?

A

20p-400nm

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8
Q

What is uv radiation broken into(give wavelengths)?

A

UVC- 200-280NM
UVB-280-320NM
UVA-320-400NM

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9
Q

How does wavelength impact UV damage to skin?

A

The shorter the wavelength the more harmful the radiation, but the less able to penetrate skin

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10
Q

How is UVB prevented from reaching terrestrial biomes?

A

By reactions with ozone in the stratosphere

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11
Q

Why is UVB so damaging?

A

It has short wavelengths and is highly energetic. This means it can cause alterations to biological molecules and has a high damage potential

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12
Q

How does UVB cause damage in humans?

A

UVB targets nucleus acids (dna,rna), which leads to tumours and skin damage. Decreases in stratospheric ozone increase human exposure to uvb.

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13
Q

How does UVB cause dna damage in plants?

A

UVB radiation penetrates plants and causes damage to: nuclear, chloroplast and mitochondrial DNA via oxidative damage, retarding the growth and development of plants

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14
Q

Is DNA damage in plants permanent? (From UVB)

A

No. When light is not limiting, dns repair mechanism are driven by uva which means the uvb impacts on plant photosynthesis proteins is limited, and plants are able to repair themselves quickly.

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15
Q

What are the key targets for UVB radiation in plants? (Four)

A
  1. Nuclei acids
  2. Amino acids
  3. Proteins (including the photosynthetic ones)
  4. Signalling hormones (uvr8 photoreceptors)
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16
Q

How does uvb radiation alter plant growth?

A

UVB may increase photosynthesis, but it damages signalling hormones which causes a reduction in plant growth

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17
Q

What are the 5 key inhibitstions to growth that occur as a result of UVB radiation damaging signalling hormones?

A
  1. Reduction in hypocotyl length
  2. Expansion of the catyledon
  3. Reduction in leaf and rosette size
  4. Stomatal closure
  5. reduction in root and shoot branching
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18
Q

How does UVB radiation impact ecosystem services as a whole?

A

“Unhealthy” uvb exposure reduces plant growth and differential plant response will alter species interaction and composition, impacting the processes within an ecosystem

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19
Q

What is reduced growth from UVB radiation a result of?

A

Damage to signalling hormones, NOT photosynthesis

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20
Q

How do plants respond to increased UVB radiation? (Hint: compounds)

A

They accumulate uvb absorbing pigments, causing an increased synthesis of phenolic compounds

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21
Q

Why are phenological compounds important? How does uvb impact them?

A

Phenological compounds are essential for plant defence against pests and pathogens. UVB increases the production of these, increasing a plants resistance to this type of predation.

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22
Q

How does changes in the secondary chemistry from plants increase ecosystems?

A

It increases their resistance to consumers/ decomposers, causing an altered condition balance and prevalence of plant species.

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23
Q

What is a indirect impact of UVB radiation in plants?c

A

Changes to nutrient cycling

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24
Q

What are they key signalling hormones targeted by UVB radiation in plants? (2)

A

UVR8 photoreceptors

IAA giberellins

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25
Q

How does increased UVB radiation damage ecosystem productivity?

A

Differential responses in plants will alter interactions and overall species composition, will will alter rates and occurrences of key ecosystem services. Ultimately the competing balance and prevalence of plant species is changed.

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26
Q

How does changes in phenolic compounds occur, and what are the implications of these?

A

Changes in phenoloic compounds occur from increasing UVB radiation penetrating plants, and an overall increase of them occurs. This then causes an increased resistance of plants to priests and pathogens, altering interacting between these parts of the ecosystem, which (due to complex interactions) will impact a variety of ecosystem interactions.

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27
Q

What is the difference between primary and secondary metabolites?

A

Primary metabolites are compounds released fro primary functions within the plant, such as carbohydrates, amino acids and sugars.

Secondary metabolites play no role in primary functions, and are instead chemical compounds primarily for protective value

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28
Q

Give an example of how uvb has altered primary and secondary plant metabolites

A

Primary- UVB radiation targets photosynthetic proteins and signally hormones, impacting growth of the plant.
Secondary- UVB radiation impacts the production of phenoloic compounds within the plant, altering their protective measures against pathogens and pests.

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29
Q

How does increased UVB radiation impact decomposers?

A

Growth and distribution of plant populations is altered, which in turn influences the decomposition potential within an ecosystem and subsequent nutrient cycling

30
Q

What type of pollutant is carbon dioxide?

A

A primary gas pollutant

31
Q

How does carbon dioxide get inside plant leaves?

A

It diffuses through the stomata and occupies the internal air spaces within plants

32
Q

What is the difference between the indirect and direct effects on plants from elevated atmospheric carbon?

A

The direct effects of atmospheric carbon impact photosynthetic process and further plant processes dependant on the products of this.
Indirect effects on plants come from the greenhouse affect and associated changes in temperatures and water availability (both required factors for growth)

33
Q

What are the direct effects of elevated carbon dioxide on cam plants?and what are they?

A

Cam plants are simply plants with a photosynthetic pathway adapted to arid conditions. It’s been found that in cam species, doubling of atmospheric Co2 causes a 35-40% increase in photosynthesis, but this increase varied MASSIVELY between species.
Doubling Co2 was also seen to cause an on average 35% increase in plant biomass

34
Q

What are the direct effects of increase Co2 on c3 plants?

A

Elevated Co2 results in there simply bring more carbon dioxide outside of plants, increasing the CONCENTRATION gradient between the leaves and outside air.
The increased gradient causes an increase in Co2 uptake, and increased photosynthesis.

35
Q

What are c3 plants?

A

C3 plants are plants that fix atmospheric carbon and produce three carbon sugars. They represent approximately 94 percent of plant species

36
Q

How is Co2 fixed within c3 plants?

A

Co2 of fielded by the protein RUBISCO. this contains the enzyme carboxylase which fixes atmospheric Co2 into phosphoglycerate. This produces sugars

37
Q

What is photorespiration?

A

Photorespiration utilised oxygen instead of Co2 in the Calvin cycle. This process uses atp rather than creating it, and produces no sugars.

38
Q

Why is photorespiration energetically wasteful? ( 4 reasons)

A
  1. It uses ATP, which could otherwise be used for growth
  2. It produces no sugars
  3. Results on an overall loss of fixed carbon, which could be utilised in ptohosynthesis
  4. Increases Co2 concentrations in the leaf, which reduces the concentration gradient within outside the leaf so reduces diffusion of Co2 for photosynthesis
39
Q

How do increasing carbon dioxide levels impact rubisco function?

A

It increases the carboxylase activity of the plant, increasing photosynthesis.
It decreases the oxygenase activity of the plant, which reduces the wasteful process of photorespiration
THIS INCREASES RUBISCO ACTIVITY

40
Q

How does the photosynthetic structure of c4 plant photosynthesis differ from c3 plants?

A

It occcurs in two distinct cells

41
Q

What are the two cells for photosynthesis in c4 plants? Give their function

A

The mesophyll
Co2 fixed via Pepc carboxylase. Atmospheric Co2 is fixed into c4 acids and then transported to the bundle sheath cells.
The bundle sheath cells
These perform normal Calvin cycle functions, breaking the c4 acids into c3 acids and Co2. Rubisco then fixed the c3 sugars via carboxylase, and these are exported from the bundle sheath to the rest of the plant .

42
Q

How does the high concentration of Co2 in the bundle and sheath cells impact rubisco?

A

Essentially, the high concentration promotes a constant state of high csrboxylase activity and suppression of oxygenase. This promotes high photosynthesis and limited photorespiration.

43
Q

In which plant is the response to elevated Co2 greater?

A

In c3 plants

44
Q

In which plant type are the effects on increased temperature greater?

A

C4 plants

45
Q

What effect does increased temperature have on c3 plants?

A

It increases oxygenase activity, increasing photorespiration. This causes an increase in realised Co2, reducing photosynthesis and overall plant productivity

46
Q

What effect does increasing temperature have on productivity of c4 plants?

A

Increases in photosynthesis are far greater as c4 plants are more “robust” meaning oxygenase in suppressed and very little change in photorespiration occurs. This means that photosynthesis can continue with minimal losses

47
Q

How does increased carbon dioxide impact stomata? What does this impact?

A

Increased Co2 results in increased stomatal closure, and reduced transpiration as a result. This reduces Co2 uptake, and the plants ability to increase photosynthetic rates in response to changing Co2 levels. Water loss via evapotranspiration is also reduced.

48
Q

What does the impact of reduced evapotranspiration (from reduced stomatal closure) have on plants?

A

It reduces their ability to cool themselves, reducing their robustness to changing climatic conditions

49
Q

What impact does changing Co2 have on stomatal density? What could this be a result of.

A

Generally, elevated Co2 is thought to cause a shift towards a low density of large stomata in plants. This is thought to be a protection method against excessive water loss.

50
Q

What is water use efficiency.

A

The yield per unit crop of water used?

51
Q

How is wue impacted by changes in stomatal closure from elevated Co2 levels?

A

Wue is increased as less water loss via transpiration can occur, with wue typicall w0-25% greater in elevated Co2 conditions.

52
Q

What has been the observed change in phenology from increased Co2 (ragweed example)

A

Faster growing rates and decreased reproductive periods

53
Q

What will differential plant responses to changes in Co2 alter? (3 factors)

A

Plant competition
Biodiversity
Ecosystem function

54
Q

Define pollutant

A

A pollutant is any chemical that is in the wrong place in the wrong concentration

55
Q

What are the two forms of air pollutants?

A

Particulate air pollutants

Gaseous air pollutant

56
Q

What are the two pollutant origins?

A
  1. Natural emissions (Volcanoes, swamps, forest fires)

2. Anthropogenic emissions (dmonestic/ industrial processes)

57
Q

What are the two modes of pollutant deposition?

A
  1. Dry deposition

2. Wet deposition

58
Q

What are the two impacts of the DRY DEPOSITION. Of nox and so2?

A

Impacts to light and dark reactions

59
Q

Why are the impacts of dry deposition greater at high latitudes?

A

Stomata are greater in size so more pollutant can enter for a given leaf size

60
Q

Explain the impacts to light reactions from the dry deposition of pollutants

A

The increase H+ content causes disruption to electron transfer, which decreases the proton gradient across the THYLAKOIDS SPACE
This proton gradient drives ATP synthesis, so a disruption effectively stops this sysnthesis and IMPACTS PLANT PROCESSES/ GROWTH

61
Q

What is the impacts of pollutant gasses on stomata?

A

Acidification of the stomata

62
Q

Detail the impacts to dark reactions from dry deposition of pollutants

A

Acidification impacts rubisco functioning and overall Co2 fixation
This reduced photosynthesis, photosynthetic production (which then impacts overall plant growth)

63
Q

Overall, what are the impacts of light and dark reactions?

A

Growth inhibition

64
Q

What is the percentage growth reduction from SO2?

A

7.5-25%

65
Q

What is the percentage growth reduction from NOx?

A

Up to 55% growth reduction

66
Q

What two things are impacted by wet deposition?

A
  1. Soils

2. Plant growth

67
Q

What are the impacts of wet deposition on plant growth?

A

Increases acidity reduces plants ability to maintain PH homeostasis, reduced fertility (from acidification) reduces nutrient availability in soil (more are leeched)

68
Q

What are the three key impacts to plants from wet pollutant deposition?

A
  1. Cuticle weathering
  2. Leaching of leaf cations
  3. Reduced leaf size- which impacts photosynthesis ability
69
Q

What are the five key impacts of secondary pollutants?

A
  1. Ozone reduction (and associated UVB impacts)
  2. Chlorotic FLECKING (damage to photosynthetic chlorophyll)
  3. Staples of dead or pigmented cells
  4. Growth suppression
  5. Early ear loss (ABSCISSION)
70
Q

What are the impacts of pollutants on photosynthesis?

A

Damage to photosynthetic AREA and APPARATUS

Lec 144 (6 decks)

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