Lecture 14: Photosynthesis & partitioning

Question 1

What is a source?

Answer 1

Anything carbon-based that provides assimilates (anything photosynthetic)

Question 2

What is a sink?

Answer 2

Anything non-photosynthetic that uses assimilates (includes developing leaves)

Question 3

How much solar energy can plants use for growth?

Answer 3

Only 4.6% of useful wavelengths actually get to be used for biomass

Question 4

What is photorespiration?

Answer 4

RuBisCO fixes oxygen in an energy-expensive reaction when CO2 levels are low within cells

Question 5

What chemicals are used in photorespiration?

Answer 5

2-phosphoglycolate must be converted (ATP needed) to be used for growth so get yield losses

Question 6

Do C4 plants have photorespiration?

Answer 6

No they have evolved to increase C around RuBisCO enzyme via spatial separation in bundle sheath cells

Question 7

What happens at too little light?

Answer 7

Etiolated and not green

Question 8

What happens at high light?

Answer 8

ROS, bleaching, death

Question 9

What is max photosynthesis

Answer 9

Pmax

Question 10

What is photoinhibition

Answer 10

excess light intensity

Question 11

What is maximum quantum yield

Answer 11

plant increase light increases efficient photosynthesis

Question 12

What is light compensation point?

Answer 12

Light intensity needed so that photosynthesis produces same energy as respiration

Question 13

What is non-photochemical quenching?

Answer 13

photosynthetic proteins absorb extra energy and release as heat

Question 14

What are the pigment molecules that absorb light

Answer 14

Xanthophylls

Question 15

Which pigment molecules can help NPQ

Answer 15

zeaxanthin which stimulates NPQ and helps more heat so less damage from too much light

Question 16

What is the issue with NPQ

Answer 16

plant over-invest and remains for too long

Question 17

What is partitioning?

Answer 17

putting C into parts of crop we eat

Question 18

Example of partitioning in wheat

Answer 18

less ears, higher grain mass

Question 19

What is harvest index?

Answer 19

mass of product/total above-ground biomass

Question 20

Case study of partitioning in sugar beets

Answer 20

partitioning in root and introduce sugar so more palatable

Question 21

Case study partitioning in raddish

Answer 21

two species with opposite edible parts combined to get all edible so double harvest index

Question 22

How is partitioning determined

Answer 22

genetics and stressors

Question 23

How are assimilates moved?

Answer 23

Passive and active

Question 24

Transportome

Answer 24

sugar transporters are specifc and important for most plant growth processes

Question 25

Partitioning of sweet11

Answer 25

sugar transporters in rice which improve yields

Question 26

How can we improve yield through photosynthesis?

Answer 26

increased proteins modified RuBisCO more responsive increased NPQ

Question 27

How can we improve yield through energy use?

Answer 27

increase for growth increase for seeds

Question 28

How can we improve yield through sugar transport?

Answer 28

increase enzyme activity increase sugar storage in cells increase sugar transport

Question 29

How can we improve yield through energy storage?

Answer 29

long term store of products larger storage organs balance of sinks and sources