Ecophysiology of plants summary
L1 Intro
Ecophysiology = study of responses of plants to ambient conditions and the causal analysis of the
corresponding ecological dependent observations
Affected = short term
Adapted = long term
Plant parts:
- Stomata = huidmondjes, at bottom of leaf
- Glandular hairs = defence
- Cuticle + epidermis = outer layer(s)
- Parenchyma = fill up cells, “flesh”
o Palisade parenchyma = long cells in leaf, on top
o Sponge parenchyma = normal sized cells in leaf, bottom
- Roothairs -> unicellar
- Stamen = male reproductive organ, creates pollen
- Stigma = female reproductive organ
- Xylem = transports water, big dead tubes, inside (orange)
- Phloem = transports sugars, smaller tubes, outside (blue)
- Pith = middle of root/stem, no vascular bundles
Stem root
L2 Acquiring resources – carbon
Resources = abiotic/biotic environmental factors that vary over time and are consumed
- Nutrient
- Space
- Water
- Light
- Carbon
Carbon -> CO2 = primary building block
CO2 -> photosynthesis -> organic molecule
Photosynthesis systems: difference in light-independent reactions
- C3: standard conditions, temperate regions
- CAM: dry & hot -> arid, desert
- C4: relatively warm & partly water-limited -> semi-arid
“normal” dark reactions
, C3 photosynthesis
Leaf: palisade + spongy parenchyma
CO2 fixation:
- during light period, together with light reactions
- by rubisco
- Relatively high photorespiration = oxygenation = bad, rubisco reacts with
oxygen instead of CO2
- (Carboxylation = opposite of oxygenation, CO2 fixation)
- At higher temperature -> higher O2/CO2 ratio -> more photorespiration -> very bad
Evolutions’ issue with rubisco:
- Used to be less of a problem: historically lower O2/CO2 ratio
- Still not suuper big problem -> only on hot day
- Maybe it’s an overflow mechanism: if dark reaction can’t keep up with light reaction
- Maybe it plays a role in nitrate metabolism -> uses amino acid
C4 photosynthesis
In warmer temps; corn/exotic grasses
Leaf: bundle sheath anatomy/ krantz anatomy
Metabolism:
- First fixes CO2 with PEP in mesophyll cell (= extra step)
- Causes high CO2 concentration, keeps rubisco functioning
- Then releases again
- CO2 used in normal calvin cycle, with rubisco, in bundle sheath
CO2 fixation:
- During light period, together with light reactions
- Almost no photorespiration
- Less energy efficient: PEP recycling costs ATP
-> moves CO2 over space
PEP doesn’t work as well in lower temperatures -> less affinity
In that case: C3 functions better
At high temp: C4 outcompetes C3: because low photorespiration
At low temp: C3 outcompetes C4: because no cold shock
C3 and C4 have different rubisco:
C4 rubisco needs higher [CO2] to function
C3 high affinity + slow rate
C4 low affinity + high max rate
PEP high affinity + Vmax
-> PEP + C3 use ambient CO2 levels, C4
uses higher concentration created by PEP
L1 Intro
Ecophysiology = study of responses of plants to ambient conditions and the causal analysis of the
corresponding ecological dependent observations
Affected = short term
Adapted = long term
Plant parts:
- Stomata = huidmondjes, at bottom of leaf
- Glandular hairs = defence
- Cuticle + epidermis = outer layer(s)
- Parenchyma = fill up cells, “flesh”
o Palisade parenchyma = long cells in leaf, on top
o Sponge parenchyma = normal sized cells in leaf, bottom
- Roothairs -> unicellar
- Stamen = male reproductive organ, creates pollen
- Stigma = female reproductive organ
- Xylem = transports water, big dead tubes, inside (orange)
- Phloem = transports sugars, smaller tubes, outside (blue)
- Pith = middle of root/stem, no vascular bundles
Stem root
L2 Acquiring resources – carbon
Resources = abiotic/biotic environmental factors that vary over time and are consumed
- Nutrient
- Space
- Water
- Light
- Carbon
Carbon -> CO2 = primary building block
CO2 -> photosynthesis -> organic molecule
Photosynthesis systems: difference in light-independent reactions
- C3: standard conditions, temperate regions
- CAM: dry & hot -> arid, desert
- C4: relatively warm & partly water-limited -> semi-arid
“normal” dark reactions
, C3 photosynthesis
Leaf: palisade + spongy parenchyma
CO2 fixation:
- during light period, together with light reactions
- by rubisco
- Relatively high photorespiration = oxygenation = bad, rubisco reacts with
oxygen instead of CO2
- (Carboxylation = opposite of oxygenation, CO2 fixation)
- At higher temperature -> higher O2/CO2 ratio -> more photorespiration -> very bad
Evolutions’ issue with rubisco:
- Used to be less of a problem: historically lower O2/CO2 ratio
- Still not suuper big problem -> only on hot day
- Maybe it’s an overflow mechanism: if dark reaction can’t keep up with light reaction
- Maybe it plays a role in nitrate metabolism -> uses amino acid
C4 photosynthesis
In warmer temps; corn/exotic grasses
Leaf: bundle sheath anatomy/ krantz anatomy
Metabolism:
- First fixes CO2 with PEP in mesophyll cell (= extra step)
- Causes high CO2 concentration, keeps rubisco functioning
- Then releases again
- CO2 used in normal calvin cycle, with rubisco, in bundle sheath
CO2 fixation:
- During light period, together with light reactions
- Almost no photorespiration
- Less energy efficient: PEP recycling costs ATP
-> moves CO2 over space
PEP doesn’t work as well in lower temperatures -> less affinity
In that case: C3 functions better
At high temp: C4 outcompetes C3: because low photorespiration
At low temp: C3 outcompetes C4: because no cold shock
C3 and C4 have different rubisco:
C4 rubisco needs higher [CO2] to function
C3 high affinity + slow rate
C4 low affinity + high max rate
PEP high affinity + Vmax
-> PEP + C3 use ambient CO2 levels, C4
uses higher concentration created by PEP
