Lecture 4 - C4 Photosynthesis

Question 1

What’s a mesophyll cell

Answer 1

Standard plant leaf cell with chloroplast

Question 2

What’s a bundle sheath?

Answer 2

Specialised plant cell around vascular bundles, has chloroplasts

Question 3

How does CO2 leave leaf in C4 photosyntehsis

Answer 3

It diffuses into air space and eventually into mesophyll cells

Question 4

What happens to CO2 in Mesophyll cells

Answer 4

CO2 is converted into bicarbonate ions then oxaloacetate

Question 5

How many C in oxaloacetate

Answer 5

4C

Question 6

What happens to oxaloacetate when produced

Answer 6

Can’t be transported within plants, so turned to malate (4C) which can move to chloroplast of bundle sheath cells

Question 7

What happens to malate after it’s converted form oxaloacetate

Answer 7

In bundle sheath cells, it gets decarboxylated into 3C (pyruvate) and CO2

Question 8

What happens to pyruvate after malate gets decarboxylated

Answer 8

Goes back to mesophyll chloroplast, converted to Phosphoenolpyruvate and then converted to HCO3 ions to produce oxaloacetate

Question 9

What’s point of C4 pathway

Answer 9

Get high concentrations of CO2 in calvin cycle from these reaction cycles

Question 10

What temp can C4 stay decent at

Answer 10

40-50 degrees

Question 11

Why is C4 able to stay good at higher temps than C3

Answer 11

Since photorespiration is less, when sped up by hot temps it’s less impactful, basically a good adaptation for high temps

Question 12

Does C4 plants increase near the equator

Answer 12

yes!

Question 13

What’s C4 plant patterns at higher alttitudes and why

Answer 13

C4 more common lower down since temperature higher, high altitudes higher rainfall and colder so C3 more dominant

Question 14

Hows C4 at water efficiency?

Answer 14

Way better than C3, like twice as good ~280-350water use efficency

Question 15

Hows C3 at water efficency?

Answer 15

Kinda lame, ~550-700ish water efficency

Question 16

When did C4 evolve in monocots

Answer 16

Around 21-35Ma

Question 17

When did C4 evolve in dicots

Answer 17

Around 15-21Ma

Question 18

How many indy origins of C4 pathway

Answer 18

like 62 WOwoWOwo tends to be in low c02 hot dry areas

Question 19

how much of earth has rice as taple grain

Answer 19

like 50%

Question 20

Is rice efficient as a C3 plant?

Answer 20

No. Rice has low light-conversion efficiency, high photorespiration. High n requirements and high water requirements.

Question 21

What would be the use of C4 rice?

Answer 21

The development of C4 rice could increase yield up to 50% and spread available conditions for rice growth.

Question 22

how to get c4 r1ce illegally?

Answer 22

genetic modfiication wooo

Question 23

What about legal C4 Rice?

Answer 23

gotta do mutagenesisis, intense radiation and hoping c4 somehow happens , luck based

Question 24

Name an important factor in developing C4 rice/

Answer 24

Get bundle sheaths closer! Decreasing the distance between the mesophyll and the bundle sheath.

Question 25

What is mutagenesis?

Answer 25

The purposeful induction of mutations via radiations, hoping some of these mutations are useful.

Question 26

Why may C4 rice be impossible?

Answer 26

Since rice always grew in standing water, there’s never been a pressure to develop into a C4 plant.

Question 27

What % NPP do the 3% of plants that are C4 carry out?

Answer 27

3% of C4 plants carry out 25% of total plant NPP.