Lecture 14: Photosynthesis & partitioning Flashcards
What is a source?
Anything carbon-based that provides assimilates (anything photosynthetic)
What is a sink?
Anything non-photosynthetic that uses assimilates (includes developing leaves)
How much solar energy can plants use for growth?
Only 4.6% of useful wavelengths actually get to be used for biomass
What is photorespiration?
RuBisCO fixes oxygen in an energy-expensive reaction when CO2 levels are low within cells
What chemicals are used in photorespiration?
2-phosphoglycolate must be converted (ATP needed) to be used for growth so get yield losses
Do C4 plants have photorespiration?
No they have evolved to increase C around RuBisCO enzyme via spatial separation in bundle sheath cells
What happens at too little light?
Etiolated and not green
What happens at high light?
ROS, bleaching, death
What is max photosynthesis
Pmax
What is photoinhibition
excess light intensity
What is maximum quantum yield
plant increase light increases efficient photosynthesis
What is light compensation point?
Light intensity needed so that photosynthesis produces same energy as respiration
What is non-photochemical quenching?
photosynthetic proteins absorb extra energy and release as heat
What are the pigment molecules that absorb light
Xanthophylls
Which pigment molecules can help NPQ
zeaxanthin which stimulates NPQ and helps more heat so less damage from too much light
What is the issue with NPQ
plant over-invest and remains for too long
What is partitioning?
putting C into parts of crop we eat
Example of partitioning in wheat
less ears, higher grain mass
What is harvest index?
mass of product/total above-ground biomass
Case study of partitioning in sugar beets
partitioning in root and introduce sugar so more palatable
Case study partitioning in raddish
two species with opposite edible parts combined to get all edible so double harvest index
How is partitioning determined
genetics and stressors
How are assimilates moved?
Passive and active
Transportome
sugar transporters are specifc and important for most plant growth processes
Partitioning of sweet11
sugar transporters in rice which improve yields
How can we improve yield through photosynthesis?
increased proteins
modified RuBisCO
more responsive
increased NPQ
How can we improve yield through energy use?
increase for growth
increase for seeds
How can we improve yield through sugar transport?
increase enzyme activity
increase sugar storage in cells
increase sugar transport
How can we improve yield through energy storage?
long term store of products
larger storage organs
balance of sinks and sources
