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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
How does photosynthesis sustain life on Earth?
Oxygenated Earth’s atmosphere, allowing complex life to develop Determines final biomass (yield) Provides the vast majority of energy for life on Earth
26
What is Rubisco?
CO2 fixing enzyme in photosynthesis
27
How common is Rubisco?
The most abundant protein on the planet
28
What happens if rubisco uses oxygen instead of carbon dioxide?
Leads to a different reaction, production of 2-phosphoglycolate
29
What does the photo respiratory cycle result in?
release of CO2 and ammonia
30
What type of process do we refer to the photorespiratory as?
A wasteful process
31
What is the impact of photorespiration on soybean and wheat yields?
Reduces by 36% and 20% respectively
32
How much would reducing photorespiration by 5% be worth annually?
$500 million
33
What are the three ways we can improve photosynthesis?
Rubisco and regulation Increasing CO2 RuBP Supply
34
What can improving Rubisco lead to?
20% improvement in photosynthetic gains per day
35
What does engineering CO2 concentrating methods do?
Reduces amount of photorespiration, and increases photosynthesis
36
How can we engineer CO2 concentrating methods?
Converting C3 and C4 crops | Optimising stomatal and mesophyll conductance
37
How can we improve photosynthesis with rubisco and regulation?
Replacing Rubisco with better performing enzymes Improving activation Optimising/improving catalytic properties
38
How does improving crop yields make us more sustainable?
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
What are the two main approaches to improving crop yield potential?
Use existing natural diversity (try find more efficient photosynthetic processes in relatives) Generate novel germplasm (genetic engineering)
40
What is the advantages of genetic engineering?
Much more precise | Frequently faster
41
What is the disadvantages of genetic engineering?
can eliminate natural variation
42
What is the disadvantages of cross breeding?
Takes longer than genetic engineering | Need to have natural variety
43
What is the advantages of cross breeding?
Maintains genetic vartiation
44
What does RIPE stand for?
Realising Increase Photosynthetic Efficiency
45
What does RIPE target photosynthetic sub-processes to do?
Harness the power of the sun Feed the world Make crops more efficient Make crops of relevance globally
46
What is the approach of the RIPE project?
to target crops of global interest, and specifically for Africa
47
What are the main crops the RIPE project targets?
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
How much more food will we need to be producing by 2050?
60%
49
What do plants do when in the brightest sunlight?
rapidly reduce productivity of photosynthesis to protect themselves
50
How much plant productivity is lost due to reducing sensitivity to the sun (and how much can we get backl)
20% of plant productivity is lost during this period | Genetic changes allowed plants to retain about 15% of their productivity
51
How much did global food production increase by from | 1960 to 2005?
160%
52
What is the problem with plant light capture?
Too efficient at absorbing small amounts of light to outcompete other plants
53
What is the benefit of plants being more efficient at converting different energy types?
then they wouldn’t be competing as much, which makes them better suited
54
What is the major limiting factor of photosynthesis?
the inefficiency of transferring captured CO2 from the airspace of leaves to the chlorophyll for photosynthesis to occur
55
What would achieving a higher concentration of CO2 in chlorophyll do?
allow a reduction in the amount of rubisco required by the plant.
56
What would lower intercellular CO2 concentration do?
would likely increase diffusive speed
57
What is the idea of a smart canopy of plants?
envisions a canopy of plants that work cooperatively to maximise potential for light harvesting and biomass production per unit area
58
What is the problem with the smart canopy concept?
this is working against natural selection, which makes the process (and the understanding needed) more complex

LEC.103 (5 decks)

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