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LEC.103 > Lecture 6 - Photosynthesis and crop improvement > Flashcards

Lecture 6 - Photosynthesis and crop improvement Flashcards

1
Q

What do we believe world population will be by 2050?

A

9 billion

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2
Q

Where is population growth mostly happening?

A

Developing countries

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3
Q

How has population changed in developed countries over the last few decades?

A

It’s remained relatively constant

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4
Q

What nullifies our lack of population growth in developed countries?

A

Extra consumption

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5
Q

What % of daily calories and proteins does wheat represent?

A

20%

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6
Q

Can we rely on rainfall for crop growth now?

A

No

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7
Q

How has crop yield changed since the 1960s and why?

A

Steadily increased - due to practices that target crop improvement

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8
Q

For every 1 degree change in climate, how much wheat yield do we lose?

A

4-6%

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9
Q

What will happen to wheat yields if we don’t increase them by 2050?

A

We will be producing less than we are now

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10
Q

What are the challenges in the way of increasing food production?

A

The rise of biofuels
Urbanisation
Climate change
Soil degradation

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11
Q

What is the overall challenges when trying to make enough food?

A

Increase crop yield sustainably
Maintain use of agricultural land (or reduce)
Reduce consumption of water, fertilisers and pesticides
Make crops resilient to climate change

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12
Q

Photosynthesis definition

A

The process in which plants use the energy from the sun in order to assimilate carbon dioxide, resulting in the production of carbohydrates (used for plant growth and for producing the products that we will harvest)

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13
Q

How does the photosynthesis process work?

A

Plants intercept the energy from the sun
Use this in light-independent reactions, and split water, resulting in the liberation of oxygen (that we breathe)
Also produces energy (ATP) - used with reducing power (also produced in reaction), then used in the subsequent reactions of photosynthesis
This is frequently called the carbon assimilation side of photosynthesis, or the light independent reactions of photosynthesis
Carbon assimilation - catalyzed by Rubisco
This leads onto the production of carbohydrates

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14
Q

What is Rubisco responsible for?

A

fixing carbon dioxide in the initial steps of the Carbon Benson Bassham cycle in carbon assimilation

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15
Q

What is the genetic yield potential formula of a crop?

A

Genetic yield potential = Solar radiation x Light interception x Conversion efficiency x Harvest Index

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16
Q

What is harvest index?

A

proportion of the total plant biomass that is in the product that we are going to harvest

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17
Q

What is the theoretical maximum and observed values of light interception

A

0.9, 0.89

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18
Q

What is the theoretical maximum and observed values of conversion efficiency

A

0.094, 0.032

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19
Q

What is the theoretical maximum and observed values of harvest index

A

0.6,0.6

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20
Q

What is the effect of increase photosynthesis on crop yields?

A

Increases them

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21
Q

How can we increase photosynthesis?

A

This can be done by increasing free air CO2 - so the plants can absorb more

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22
Q

What is the problem with just focussing on maximising photosynthesis?

A

we won’t get the maximum potential increase in crop yields

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23
Q

What do researchers need to do to maximise crop yields?

A

Collaborate

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24
Q

Where does photosynthesis take place in plants?

A

The leaves and stem - in the chloroplast

25
Q

How does photosynthesis sustain life on Earth?

A

Oxygenated Earth’s atmosphere, allowing complex life to develop
Determines final biomass (yield)
Provides the vast majority of energy for life on Earth

26
Q

What is Rubisco?

A

CO2 fixing enzyme in photosynthesis

27
Q

How common is Rubisco?

A

The most abundant protein on the planet

28
Q

What happens if rubisco uses oxygen instead of carbon dioxide?

A

Leads to a different reaction, production of 2-phosphoglycolate

29
Q

What does the photo respiratory cycle result in?

A

release of CO2 and ammonia

30
Q

What type of process do we refer to the photorespiratory as?

A

A wasteful process

31
Q

What is the impact of photorespiration on soybean and wheat yields?

A

Reduces by 36% and 20% respectively

32
Q

How much would reducing photorespiration by 5% be worth annually?

A

$500 million

33
Q

What are the three ways we can improve photosynthesis?

A

Rubisco and regulation
Increasing CO2
RuBP Supply

34
Q

What can improving Rubisco lead to?

A

20% improvement in photosynthetic gains per day

35
Q

What does engineering CO2 concentrating methods do?

A

Reduces amount of photorespiration, and increases photosynthesis

36
Q

How can we engineer CO2 concentrating methods?

A

Converting C3 and C4 crops

Optimising stomatal and mesophyll conductance

37
Q

How can we improve photosynthesis with rubisco and regulation?

A

Replacing Rubisco with better performing enzymes
Improving activation
Optimising/improving catalytic properties

38
Q

How does improving crop yields make us more sustainable?

A

More agricultural land - more yield per hectare, more space for biodiversity
Use water more efficiently
Ned lower inputs (fertilisers) - lower costs for farmers, better soil and more sustainable

39
Q

What are the two main approaches to improving crop yield potential?

A

Use existing natural diversity (try find more efficient photosynthetic processes in relatives)
Generate novel germplasm (genetic engineering)

40
Q

What is the advantages of genetic engineering?

A

Much more precise

Frequently faster

41
Q

What is the disadvantages of genetic engineering?

A

can eliminate natural variation

42
Q

What is the disadvantages of cross breeding?

A

Takes longer than genetic engineering

Need to have natural variety

43
Q

What is the advantages of cross breeding?

A

Maintains genetic vartiation

44
Q

What does RIPE stand for?

A

Realising Increase Photosynthetic Efficiency

45
Q

What does RIPE target photosynthetic sub-processes to do?

A

Harness the power of the sun
Feed the world
Make crops more efficient
Make crops of relevance globally

46
Q

What is the approach of the RIPE project?

A

to target crops of global interest, and specifically for Africa

47
Q

What are the main crops the RIPE project targets?

A

Rice (top source of human calories) and Cassava (top source of calories in Sub-Saharan Africa) also targeting Soy bean and cowpea, both major sources of vegetable protein worldwide

48
Q

How much more food will we need to be producing by 2050?

A

60%

49
Q

What do plants do when in the brightest sunlight?

A

rapidly reduce productivity of photosynthesis to protect themselves

50
Q

How much plant productivity is lost due to reducing sensitivity to the sun (and how much can we get backl)

A

20% of plant productivity is lost during this period

Genetic changes allowed plants to retain about 15% of their productivity

51
Q

How much did global food production increase by from

1960 to 2005?

A

160%

52
Q

What is the problem with plant light capture?

A

Too efficient at absorbing small amounts of light to outcompete other plants

53
Q

What is the benefit of plants being more efficient at converting different energy types?

A

then they wouldn’t be competing as much, which makes them better suited

54
Q

What is the major limiting factor of photosynthesis?

A

the inefficiency of transferring captured CO2 from the airspace of leaves to the chlorophyll for photosynthesis to occur

55
Q

What would achieving a higher concentration of CO2 in chlorophyll do?

A

allow a reduction in the amount of rubisco required by the plant.

56
Q

What would lower intercellular CO2 concentration do?

A

would likely increase diffusive speed

57
Q

What is the idea of a smart canopy of plants?

A

envisions a canopy of plants that work cooperatively to maximise potential for light harvesting and biomass production per unit area

58
Q

What is the problem with the smart canopy concept?

A

this is working against natural selection, which makes the process (and the understanding needed) more complex

LEC.103 (5 decks)

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