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MMCCQQ22 > L23 Temperature as a Limiting Factor in PS and Crop Production > Flashcards

L23 Temperature as a Limiting Factor in PS and Crop Production Flashcards

1
Q

what are the main factors limiting primary production?

A

water and temperature stress

light and mineral elements in soil

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2
Q

what metabolic solutions have plants evolved to temperature and water stress?

A

temp - generating internal heat

water - closing stomata during the day

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3
Q

how much of the 100% solar radiation is actually used by plant?

A

24%

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4
Q

how much solar energy is used to produce carbohydrate sugars?

A

19% of solar energy is lost during metabolism

5% goes towards making carbohydrates

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5
Q

why are solar panels ‘more efficient’ at absorbing/ using solar energy?

A

they use less ~11-15% and they only prodce hydrogen as a by-product not complex carbohydrate

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6
Q

what causes decreased yields in crop production?

A

plants not being accurately adapted to their introduced climate and soil conditions (temp and water stress)

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7
Q

where is the highest concentration of cholorophyll/ rate of photosynthesis/ primary production observed?

A

less extremes in temperature (10-20degrees) and maximum rainfall

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8
Q

what plant can grow at low temps -5 to 5 degrees?

A

ice algae

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9
Q

what plant can grow at mid temps 10 to 40 degrees?

A

maize

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10
Q

what plant can grow at high temps 45 to 50 degrees?

A

thermophilic algae

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11
Q

what environmental signals turn plant metabolism off?

A

day length shortening and temperature decrease

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12
Q

how do plants survive freezing temperatures?

A

1) remove water from cytoplasm in pre-dormancy period (cellular structures cannot freeze and will not be damaged)
2) flood cytoplasm vacuole with carbohydrate and proteins which lower freezing point

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13
Q

what are ‘anti freeze molecules’ in plants?

A

carbohydrate storage in vacuoles

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14
Q

when do heat shock proteins become activated?

A

in stress conditions - extreme temperatures

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15
Q

what are heatshock proteins?

A

they are chaperones that control the aggregation and misfolding of proteins

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16
Q

what are the weight classes of heat shock proteins?

A

HSP100, HSP90, HSP70 and HSP 60

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17
Q

what 2 processes share a common pathway?

A

photosynthesis and transpiration

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18
Q

where does gaseous diffusion occur in the plant?

A

stomata openings

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19
Q

what gradient helps with CO2 diffusion into the plant?

A

water within the plant versus outside of the plant - this is because when stomata are open water is lost

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20
Q

what abiotic factor influences opening and closing of stomata?

A

temperature

21
Q

how much water is lost during photosynthesis?

A

250-500 moles

22
Q

when water is lost from the leaves what else happens?

A

heat loss

23
Q

what happens during the Calvin cycle?

A

CO2 is converted into sugar

24
Q

Describe C3 plants

A

they have a low water use efficiency

25
Q

why can water loss/ transpiration be beneficial to plants?

A

it is a means of heatloss

26
Q

what enzyme converts CO2 into sugar during Calvin cycle?

A

rubisco

27
Q

Describe rubisco

A

large mass - 560kDa

very slow acting

28
Q

what happens if we add more rubisco enzymes to plants?

A

no effect

29
Q

what happens if oxygen is used in photosynthesis instead of CO2?

A

we get 2 carbon acid instead of a 3 carbon sugar, metabolic dead end because it cannot enter calvin cycle

30
Q

what is produced when rubisco breaks down CO2?

A

2 phosphoglycerate molecules (3 carbon sugars) that can enter calvin cycle

31
Q

where does the rubisco and CO2 carboxylation reaction occur?

A

choroplast with help of proxy zone and mitochondria

32
Q

what is produced when rubisco reacts with oxygen during oxygenation?

A

phosphoglycerate and phosphoglycollate (can’t enter Calvin Cycle)

33
Q

what occurs during ‘photo respiration’?

A
  • carboxylation and oxygenation
  • ruBP acts on CO2 to make 2 phosphoglycerate molecules
  • ruBP acts on O2 to make 1 phosphoglycerate and 1 phosphoglycollate
34
Q

how do you inactivate photorespiration pathway?

A

increase O2 production

35
Q

how do C4 plants overcome photorespiration?

A

they increase CO2 concentration at active site of rubisco enzyme

36
Q

what enzyme is more efficient than rubisco and why?

A

phosphoenol pyruvate carboxylase (PEPco), produces 4 carbon acids while knocking off photo respiration allowing high rates of sugar production

37
Q

what is photorespiration?

A

a respiratory process in which plants take up oxygen in the light and give out some carbon dioxide, contrary to the general pattern of photosynthesis

38
Q

what are C3 plants?

A

plants that use C3 pathway to convert CO2 into 3-phosphoglycerate for Calvin Cycle

39
Q

what are C4 plants?

A

plants that use C4 pathway to produce oxaloacetic acid for Calvin Cycle

40
Q

examples of C3 plants

A

oats, ryes, wheats, rice, cotton, sunflower

41
Q

examples of C4 plants

A

maize, sugar cane, desert succulents

42
Q

what is the relationship between heat generation and respiration in the spadix?

A

linear - as rate of respiration increases, rate of thermogenesis increases

43
Q

how can respiratory systems support high rates of thermogenesis when limiting in ADP?

A

ADP is uncoupled from cellular respiration

44
Q

how can we measure the rate of photosynthesis?

A

monitoring dissolved oxygen

45
Q

what initiates oxygen reduction to H2O in photosynthesis?

A

succinate

46
Q

what does SHAM inhibit?

A

cyanide resistant pathway in photosynthesis

47
Q

what does cyanide inhibit?

A

electron flow through ETC cytochromes

48
Q

what does addition of ADP do?

A

facilitates formation of proton gradient - oxygen is uptaken/ decreases significantly
rate of respiration doubles

49
Q

what allows plants to generate heat quickly?

A

uncoupling respiration ETC from ATP and using alternative oxidase which is cyanide insensitive but sensitive to SHAM

MMCCQQ22 (14 decks)

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