Resources - CO2 and Minerals

Question 1

How do plants source carbon?

Answer 1

Atmospheric CO2, organic matter decomposition.

Question 2

How does CO2 diurnally change?

Answer 2

Upward flux at night to downward flux in the day

Question 3

How does CO2 spatially distrubite?

Answer 3

Decreased from ground to canopy relfectiong plant prouciton and organism respiration.

Question 4

What are the three types of photosynthesis?

Answer 4

Calvin-Benson Cycles
Hatch-Slack Cycles
Crassulacean Acid Metabolism

Question 5

Calvin Benson Cycle

Answer 5

This is the fixation of CO2 with ribulose 1,5-BP into three carbon acids using RUBISCO

Question 6

Rubisco

Answer 6

Ribulose 1,5-BP Carboxylase Oxygenase catalyses CO2 addition to ribulose 1,5-BP generating two 3-PGA

Question 7

Photorespiration

Answer 7

The evolution of CO2 in PS due to the variable oxygenase/carboxylase activity of RUBISCO

Question 8

How does C3 relate to temperautre?

Answer 8

Photorespiraiton increases whilst carbon fixation efficiency decreases

Question 9

How does C3 PS relate to radiation?

Answer 9

Increasing, however it plateaus, occuring quicker in shaded species, far below full solar intensity

Question 10

Why does C3 plants have lower water efficiency?

Answer 10

Slow diffusion rates of CO2 through stomata meaning water evaporation increases.

Question 11

How may CO2 uptake in C3 be limited?

Answer 11

Rubisco production

Question 12

Hatch-Stack Cycle

Answer 12

This is CO2 diffusion into mesophyll cells, combining wiht PEP by PEP carboxylase, then entry into the C3 pathway.

Question 13

Advantages to the C4 pathway?

Answer 13

Absorbs CO2 more quickly thus reduced stomatal opening, thus photosynthesis less dependent on CO2 concentrations.
Decreased loss of CO2 during photorespiration

Question 14

What plants use C4?

Answer 14

Sorghum, Corn, Sugarcana, Millet, switchgrass, maize and main arid grasses.

Question 15

Advantage of PEP carboxylase over RUBISCO?

Answer 15

Has higher affinity for CO2

Question 16

Why are C4 plants predated less?

Answer 16

They have far less rubisco, thus less nitrogen, thus unfavourable.

Question 17

What are the disadvantages of C4?

Answer 17

Higher light compensation point thus inefficient low light intesnsities, unable to inhabit the shade

Question 18

Crassulacean Acid Metabolism

Answer 18

This is the opening of stomata at night for CO2 for decreased evaporaiton, with rubisco fixation during the day.

Question 19

How does CAM store CO2?

Answer 19

As malic acid at night.

Question 20

Advantage to CAM…

Answer 20

Photorespiration and preventing water loss by closure of stomata during day.

Question 21

How much of assimialted terrestial CO2 does C4 and CAM account for?

Answer 21

18-30%

Question 22

Varuability of CO2 effects on plants…

Answer 22

C4 and CAM are limited by other resources, whilst C3 photosynthetic rate does increase.

Question 23

How is CO2 effects on plants experimentally tested?

Answer 23

Free Air Co2 Enrichment Experiments

Question 24

Generally how does FACE work?

Answer 24

Pipes mediate CO2 icnrease at a specificed rate by computer-controlled systems.

Question 25

Relation of water loss to increasing CO2..

Answer 25

In some plants increasing CO2 means faster assimiliation meaning less stomata opening times.

Question 26

How does CO2 enrichment change plant composition?

Answer 26

Reduce nitrogen, thus proteins, with effects on plant-animal interacitons.

Question 27

Sources of nitrogen for plants…

Answer 27

Inorganic like ammonium and nitrate salts or organic from urea, peptides and amino acids.

Question 28

Main source of nitrogen for higher plants?

Answer 28

Nitrate salts as microrganisms often compete for ammonia

Question 29

Major source of nutrient acquisition for plants?

Answer 29

Mycorrhizal fungal association

Question 30

Why might P be limiting despite being abundant?

Answer 30

Forming inert complexes with Fe and Al or made immobile by binding to soil colloids.

Question 31

How might plants increase P absorption?

Answer 31

Mycorrhizae with threads extending beyond root hairs or cluster roots with carboxylate release to mobilise phosphate.

Question 32

Waterloggin of plants?

Answer 32

Failutre of plant growth and mineral uptake due to decrease diffusivity of O2.