SAS Week 5
What happens long term after the initial burst of carbon assimilation and growth experienced by C3 plants when first exposed to CO2 enrichment?
Growth and carbon assimilation eventually slow down
Are terrestrial CO2 changes are proportional to O2 fluctuations?
Yes
Do Plants vary in relative dependence on NH4+ and NO3- as sources of nitrogen from the soil? What about when Nitrogen is scarce?
Yes When N is scarce, plants incorporate whatever they can find → balance between NH4+ and NO3- usage varies w relative availability in the soil
GCMs predict that atmospheric O2 concentrations will ___________ in the future
decrease Based on the ratios between O2 and CO2 fluxes Decline in average global o2 concentrations 1993-2003 abt 25 ppm
As atmospheric CO2 concentrations rise, protein levels in crop plants ______________ and their nutritional value will be _____________________ than now.
decrease, lower than now
Plant N status _______ under CO2 enrichment
decreases
Deep waters tend to be more __________ in O2 bc, respiration and other rxns consume O2 while limiting mixing w atmosphere
deficient
Mosquito repellants work through
interfering w insect carbon dioxide sensors
Benefits of C4 carbon fixation
low atmospheric CO2 concentration and high temp do not inhibit photosynthetic sugar production as severely as in C3 plants
Air spaces within a leaf are saturated with water _______ bc cells that line the air spaces must be permeable to H2O in order for gases to _______ or ______
vapor, enter or exit
Plants must balance ______ loss with _______ gain.
water loss with carbon dioxide gain
CO2 levels relatively low 8-6 mil years ago, sp ...?
→ favor proliferation of plant species with C4 carbon fixation
As plants dependent on NO3- as a N source becomes deprived of protein what happens?
→ nutritive value of plant material will suffer
In photosynthesis, plants release ___ molecule and 1.2 molecules of O2 for every molecule of CO2 they consume
1.0
Plants respiring = consumes ____molecules of O2 for every molecule CO2 released if they are using ammonium
1.1
Point at which C3 and C4 plants are equally efficient in converting light to chemical energy falls between __-__C
20-30C
C4 plants lose ______-_______molecules of water for every molecule carbon dioxide
200-300
CO2 concentrations now exceed any that have occurred in the last ____ mil years
23
The last time atmospheric CO2 concentration exceeded 00.4% was ____ million years ago.
23 million years ago
C3 plants lose _____-_________molecules of water for every molecule carbon dioxide
500-1000
How does the additional energy from increased CO2 affect soil microorganisms?
Additional energy → soil microorganisms become more active (respiring 18% faster) → remove more nutrients from soil (iron and molybdenum) req for N fixation→ becomes scarce and lowers fixation rates
T/F Plants Rapidly convert ammonium near site of absorption. Roots absorb ammonium from the soil. High levels of ammonium are poisonous to plants Plants convert ammonium into amino acids.
All are true
How C4 Came to be
Atmospheric co2 conditions diminished to half the current level during past ice ages - RuBP carboxylation decreased and oxygenation increased→ CO2 pumping mechanism known as C4 carbon fixation
The balance between plant nitrate and ammonium use depends on their ____________ in ______________.
Availability in soils
Which has more availability? NO3- or NH4+? WHY
Availability of NO3- exceeds NH4+ by a factor of 10 NO3- moves freely through the soil than NH4+ bc it is a negative ion and does not mind to soil particles which have negatively charged surface
What most determines plant responses to elevated CO2 concentration?
Availability of soil mineral N determines plant responses to elevated CO2 concentration more than any other factor
What is the response of forests to elevated CO2?
Because forests use ammonium rather than nitrate, their growth rate will increase
The majority of studies on plants responses to CO2 enrichment has been conducted on _______ trees.
C3
Why do C4 plants lose less molecules of water for every molecule of CO2?
C4 plants operate at lower CO2 concentrations and have smaller stomatal apertures
C3 photosynthesis is favored at high ____ C4 photosynthesis is favored at high ______________
CO2 Temperatures
Terrestrial plants must expose internal organs to atmosphere for _______ to enter but lets _________ escape through stomata → plants regulate gas exchange
CO2 to enter, but lets H2O escape through stomata
meta-analysis
Combines results from independent studies to create experimental sample size and thus enhanced e the strength of statistical tests
Legumes use microbes in their root nodules to fix nitrogen from the air to useable forms
Major source of nitrogen in agricultural applications
Major sources of mineral N in solids are ?
Major sources of mineral N in solids are biological nitrogen fixation and nitrogen mineralization
The CO2 concentration exhaled from lungs (4 things)
May cause loss of consciousness May cause loss of mental acuity exceeds atmospheric CO2 concentrations during ice ages exceeds atmospheric CO2 concentrations that are likely to occur by 2010
How do plants acquire the majority of their mineral nitrogen?
Most acquire the majority of their mineral nitrogen through root absorption of NH4+ and NO3- dissolved in the soil solution
nitrogen fixing microorganisms
Most common is the pea family and rhizobia - fixes nitrogen in root area
Do most plants prefer NH4+ or NO3- ?
Most plants prefer NH4+ bc it only reqs 2 ATP Preference for NH4+ more pronounced in communities where light energy is limiting (forests)
What is usually a plants primary nitrogen source?
NO3- is often their primary nitrogen source
__________________ (N) is the mineral element that organisms req in the greatest amts
Nitrogen
Plants responses to CO2 enrichment depends on ____________________________________________ more than any other factor
Nitrogen availability from the soil
Warming or arctic region will push wheat and corn belts further ___________
Northward Because warming up → areas where those temps are found go upwards parallel
Under CO2 enrichment, plants grow ______ and release more ___________.
Plants under CO2 enrichment gen grow faster and release more carbohydrates
What is the resource triangle? What are the three categories?
Resources vital to plants and other living organisms fall into three categories: energy (carbon or light), water, nutrients Plants may use up stores of one resource to acquire additional amts of another resource is this second resource limits their growth
How does rising atmospheric CO2 affect availability of energy and water resources?
Rising atmospheric CO2→ availability of energy (carbon) and water resources increase and stimulate plant growth
What are some ways CO2-sening organisms use their ability?
Social insects use CO2 levels to determine that the hive needs more ventilation Insect herbivores use low CO2 levels to determine which plant parts are most active mushrooms use CO2 levels to determine their height above ground Plants use CO2 levels to regulate the apertures of the holes in their leaves
How will plants respond to favorable conditions? (Decrease stomatal apertures and open to the same extent)
Strategy 1: decrease stomatal apertures to conserve water while maintaining similar CO2 concentrations within their leaves (assimilation CO2 at similar rates) Strategy 2: open stomata to same extent and lose water at similar rates but increase CO2 concentration within leaves (accelerating CO2 assimilation)
How did plants develop to be competitive for nitrogen?
To be competitive plants developed diverse mechanisms for scavenging nitrogen forms as quickly as possible
Initial C3 exposure to elevated CO2 concentration stimulates net CO2 assimilation but prolonged exposure slows it down (T/F)
True
T/F: Nitrate is a component in many chemical explosives
True
CO2 is denser than air at sea level (T/F)
True any CO2 added with remain closer to ground until assimilation
Frick's First law of diffusion
a gas moves from regions of high concentration to regions of low concentration at a rate that is proportional to the concentration gradient
Cost of C4 carbon fixation
additional chemical reactions in this cycle expend two ATP per CO2 molecule pumped from the mesophyll to the bundle sheath C4 carbon fixation requires special anatomical features such as tightly packed bundle sheath cells to maintain large diff in CO2 concentrations within parts of the leaf
Lots of N in atmosphere but most organisms _______ access because of a stable triple covalent bond that makes it an inert gas
cant
Biological nitrogen fixation
certain bacteria and blue-green algae also convert N2 into NH3 (ammonia) Prod of two NH3 reqs 16 ATP (a huge amount)
Nitrogen fixation
chemical rxns of high energetic proportions enough to break the triple bond mentioned above
Photosynthesis in higher plants occurs in a specialized compartment called the
chloroplast
CO2 acclimation
decline in stimulation of net CO2 assimilation and growth by CO2 enrichment
N availability to plants _____________ under CO2 enrichment
decreases Influence of CO2 enrichment on photosynthesis depends strongly on influence on plant N status
Net CO2 assimilation
diff between CO2 consumed during photosynthetic carbon fixation that released during respiration
Doubling CO2 concentration ________ ratio of concentration gradient→ drive H2O vapor out of leaf to drive CO2 into it
diminishes
Diff effects of CO2 on NH4+ and NO3- assimilation explain ...?
ecosystem responses to CO2 enrichment Ecosystems w NH4+ as main source of N show consistent stimulation under CO2 Ecosystems w NO3- as predominant N source become deprived of protein at elevated CO2 concentration and show small changes in productivity
Stomata control based on?
elative humidity, light level, CO2 concentration, soil H2O availability to minimize H2O lost per CO2
Costs vs benefits of C4 carbon fixation depends on ______________________
environmental conditions
What is Rubisco?
enzyme that comprises up to 50% of all protein in leaves + most prevalent protein on the planet ; catalyzes first rxn of pathway
Water smaller and denser than CO2 - so it leaves leaf _____________
faster
Carbon fixation w Rubisco in C3 plants is ________w light 12CO2 versus heavy 13CO2 C3 contains a much _____ proportion of heavy carbon isotope than C4 plants
faster, smaller
C4 close stomata and conserve H2O (Strategy 1) to a ____________ extent that C3 plants
greater
Open-top chambers
have sides of transparent plastic film and large fans that blow a specified CO3 concentration into the chamber as well as regulate inside/outside temp
Changes in plant N levels also affect other herbivores such as insects due to higher CO2 concentration. How does it affect them?
herbivores→ will exp slower growth rates, lower fecundity, higher mortality (overall decline of pops bc of CO2 enrichment)
Photorespiration is responsible for the ________ efficiency of C3 plants in comparison to C4 plants
high
Rubisco has a _________ affinity for CO2 → catalyzes 2-3 more cycles of CO2 for every cycle of carbon
higher
Do higher or lower concentrations favor C4? Do higher or lower temp favor C4?
higher growing temp and low concentration favors C4
Enzymatic properties of Rubisco shift w temperature, so _________ temps favor ____________________________over carbon fixation
higher, photorespiration
Regardless of which fixation pathway a plant employs, rising atmospheric CO2 concentrations will ________________its water use efficiency
improve , because rising atmosphere increase amt of CO2 assimilated for into carbohydrate per H2O lost
CO2 enrichment ___________NO3- assimilation directly
inhibits
Weighted means =
larger studies or those with greater experimental consistency (smaller variation) have a stronger influence on the final value than smaller studies
Carbon fixation in C4 plants is ________ sensitive to carbon concentration
less
Trees tend to conserve ______ H2O and assimilate CO2 to a ____________ extent than grasses, legumes ,etc.
less, greater
In the leaves of C4 plants, CO2 enters a _____________cell → dissolves in H2o2 and forms HCO3- (___________)
mesophyll, bicarbonate
Combining and analyzing results from many different studies is called
meta-analysis
Haber-Bosch process
molecular nitrogen and hydrogen when subj to elevated temperatures (400-650C) and high pressure (200-400 atmospheres) and a metal catalyst form ammonia
Conversion of nitrate and then ammonium into amino acids expends _______ energy than most biochemical processes.
more
Fluctuations in atmospheric concentration of Co2 are smaller in amplitude O2 bc Co2 is ___________soluble in water than O2
more
Nitrogen conversion into amino acids expends __________ energy than that of ammonium.
more
Lower atmospheric CO2 concentrations led to ___________ C4 plants and a shift in herbivores because the nitrogen in C4 plants is _____________ available to herbivores than in C3 plants.
more, less
Bloom's hypothesis?
photorespiration is not just a process that consumes sugars and generates waste heat
Major sink for mineral N is N immobilization, which is ...?
process which soil microorganisms incorporate mineral N and diminish its availability to other organisms CO2 enrichment → N immobilization increases 22%
The diffusion rate of a substance is ________________to its density
proportional
Comparison between CO2 and O2 fluctuations provides estimate of what?
provides estimate of relative amounts of CO2 sequestered in ocean vs sequestered on land
Are major sources of N independent of atmospheric CO2 concentration?
Generally independent of atmospheric CO2 concentration but N fixation may decrease under CO2 enrichment if soils do not receive additional nutrients
Why are High levels NH4+ dangerous to plants?
High levels NH4+ dangerous to plants bc interferes with energy metabolism within cells Plants attempt to prevent his in their tissues; they assimilate NH4+ amino acid near site of absorption - Rapidly place any excess into vacuoles
Do higher or lower concentrations favor C3? Do higher or lower temp favor C3?
Higher CO2 concentrations and lower temp favors C3
What is the short-term response of plants to elevated atmospheric carbon concentration?
Increased carbon fixation and increased growth
What proves that herbivore populations shifted during times of low CO2 concentration 6-8 million years ago?
The crowns of teeth from herbivores began to become higher The ratio of carbon isotopes in horse teeth shifted
FACE plot
ring of 24-32 vertical standing vent pipes in a grass land or etc
During summer - atmospheric O2 concentrations (rises or lowers)? as enhanced photosynthesis releases (more or less)? O2 to air
rises, more
What is the Calvin-Benson cycle/ C3 carbon fixation pathway?
the process photosynthetic organisms follow to convert ATP and NADPH into sugars
