L23 Temperature as a Limiting Factor in PS and Crop Production

Question 1

what are the main factors limiting primary production?

Answer 1

water and temperature stress

light and mineral elements in soil

Question 2

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

Answer 2

temp - generating internal heat

water - closing stomata during the day

Question 3

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

Answer 3

24%

Question 4

how much solar energy is used to produce carbohydrate sugars?

Answer 4

19% of solar energy is lost during metabolism

5% goes towards making carbohydrates

Question 5

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

Answer 5

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

Question 6

what causes decreased yields in crop production?

Answer 6

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

Question 7

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

Answer 7

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

Question 8

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

Answer 8

ice algae

Question 9

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

Answer 9

maize

Question 10

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

Answer 10

thermophilic algae

Question 11

what environmental signals turn plant metabolism off?

Answer 11

day length shortening and temperature decrease

Question 12

how do plants survive freezing temperatures?

Answer 12

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

Question 13

what are ‘anti freeze molecules’ in plants?

Answer 13

carbohydrate storage in vacuoles

Question 14

when do heat shock proteins become activated?

Answer 14

in stress conditions - extreme temperatures

Question 15

what are heatshock proteins?

Answer 15

they are chaperones that control the aggregation and misfolding of proteins

Question 16

what are the weight classes of heat shock proteins?

Answer 16

HSP100, HSP90, HSP70 and HSP 60

Question 17

what 2 processes share a common pathway?

Answer 17

photosynthesis and transpiration

Question 18

where does gaseous diffusion occur in the plant?

Answer 18

stomata openings

Question 19

what gradient helps with CO2 diffusion into the plant?

Answer 19

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

Question 20

what abiotic factor influences opening and closing of stomata?

Answer 20

temperature

Question 21

how much water is lost during photosynthesis?

Answer 21

250-500 moles

Question 22

when water is lost from the leaves what else happens?

Answer 22

heat loss

Question 23

what happens during the Calvin cycle?

Answer 23

CO2 is converted into sugar

Question 24

Describe C3 plants

Answer 24

they have a low water use efficiency

Question 25

why can water loss/ transpiration be beneficial to plants?

Answer 25

it is a means of heatloss

Question 26

what enzyme converts CO2 into sugar during Calvin cycle?

Answer 26

rubisco

Question 27

Describe rubisco

Answer 27

large mass - 560kDa | very slow acting

Question 28

what happens if we add more rubisco enzymes to plants?

Answer 28

no effect

Question 29

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

Answer 29

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

Question 30

what is produced when rubisco breaks down CO2?

Answer 30

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

Question 31

where does the rubisco and CO2 carboxylation reaction occur?

Answer 31

choroplast with help of proxy zone and mitochondria

Question 32

what is produced when rubisco reacts with oxygen during oxygenation?

Answer 32

phosphoglycerate and phosphoglycollate (can't enter Calvin Cycle)

Question 33

what occurs during 'photo respiration'?

Answer 33

- carboxylation and oxygenation - ruBP acts on CO2 to make 2 phosphoglycerate molecules - ruBP acts on O2 to make 1 phosphoglycerate and 1 phosphoglycollate

Question 34

how do you inactivate photorespiration pathway?

Answer 34

increase O2 production

Question 35

how do C4 plants overcome photorespiration?

Answer 35

they increase CO2 concentration at active site of rubisco enzyme

Question 36

what enzyme is more efficient than rubisco and why?

Answer 36

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

Question 37

what is photorespiration?

Answer 37

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

Question 38

what are C3 plants?

Answer 38

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

Question 39

what are C4 plants?

Answer 39

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

Question 40

examples of C3 plants

Answer 40

oats, ryes, wheats, rice, cotton, sunflower

Question 41

examples of C4 plants

Answer 41

maize, sugar cane, desert succulents

Question 42

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

Answer 42

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

Question 43

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

Answer 43

ADP is uncoupled from cellular respiration

Question 44

how can we measure the rate of photosynthesis?

Answer 44

monitoring dissolved oxygen

Question 45

what initiates oxygen reduction to H2O in photosynthesis?

Answer 45

succinate

Question 46

what does SHAM inhibit?

Answer 46

cyanide resistant pathway in photosynthesis

Question 47

what does cyanide inhibit?

Answer 47

electron flow through ETC cytochromes

Question 48

what does addition of ADP do?

Answer 48

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

Question 49

what allows plants to generate heat quickly?

Answer 49

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