Resources - CO2 and Minerals Flashcards
How do plants source carbon?
Atmospheric CO2, organic matter decomposition.
How does CO2 diurnally change?
Upward flux at night to downward flux in the day
How does CO2 spatially distrubite?
Decreased from ground to canopy relfectiong plant prouciton and organism respiration.
What are the three types of photosynthesis?
Calvin-Benson Cycles
Hatch-Slack Cycles
Crassulacean Acid Metabolism
Calvin Benson Cycle
This is the fixation of CO2 with ribulose 1,5-BP into three carbon acids using RUBISCO
Rubisco
Ribulose 1,5-BP Carboxylase Oxygenase catalyses CO2 addition to ribulose 1,5-BP generating two 3-PGA
Photorespiration
The evolution of CO2 in PS due to the variable oxygenase/carboxylase activity of RUBISCO
How does C3 relate to temperautre?
Photorespiraiton increases whilst carbon fixation efficiency decreases
How does C3 PS relate to radiation?
Increasing, however it plateaus, occuring quicker in shaded species, far below full solar intensity
Why does C3 plants have lower water efficiency?
Slow diffusion rates of CO2 through stomata meaning water evaporation increases.
How may CO2 uptake in C3 be limited?
Rubisco production
Hatch-Stack Cycle
This is CO2 diffusion into mesophyll cells, combining wiht PEP by PEP carboxylase, then entry into the C3 pathway.
Advantages to the C4 pathway?
Absorbs CO2 more quickly thus reduced stomatal opening, thus photosynthesis less dependent on CO2 concentrations.
Decreased loss of CO2 during photorespiration
What plants use C4?
Sorghum, Corn, Sugarcana, Millet, switchgrass, maize and main arid grasses.
Advantage of PEP carboxylase over RUBISCO?
Has higher affinity for CO2
Why are C4 plants predated less?
They have far less rubisco, thus less nitrogen, thus unfavourable.
What are the disadvantages of C4?
Higher light compensation point thus inefficient low light intesnsities, unable to inhabit the shade
Crassulacean Acid Metabolism
This is the opening of stomata at night for CO2 for decreased evaporaiton, with rubisco fixation during the day.
How does CAM store CO2?
As malic acid at night.
Advantage to CAM…
Photorespiration and preventing water loss by closure of stomata during day.
How much of assimialted terrestial CO2 does C4 and CAM account for?
18-30%
Varuability of CO2 effects on plants…
C4 and CAM are limited by other resources, whilst C3 photosynthetic rate does increase.
How is CO2 effects on plants experimentally tested?
Free Air Co2 Enrichment Experiments
Generally how does FACE work?
Pipes mediate CO2 icnrease at a specificed rate by computer-controlled systems.
Relation of water loss to increasing CO2..
In some plants increasing CO2 means faster assimiliation meaning less stomata opening times.
How does CO2 enrichment change plant composition?
Reduce nitrogen, thus proteins, with effects on plant-animal interacitons.
Sources of nitrogen for plants…
Inorganic like ammonium and nitrate salts or organic from urea, peptides and amino acids.
Main source of nitrogen for higher plants?
Nitrate salts as microrganisms often compete for ammonia
Major source of nutrient acquisition for plants?
Mycorrhizal fungal association
Why might P be limiting despite being abundant?
Forming inert complexes with Fe and Al or made immobile by binding to soil colloids.
How might plants increase P absorption?
Mycorrhizae with threads extending beyond root hairs or cluster roots with carboxylate release to mobilise phosphate.
Waterloggin of plants?
Failutre of plant growth and mineral uptake due to decrease diffusivity of O2.
