Ch. 2 Photosynthesis (Ps) and Light. C 4 Photosynthesis 3 patterns: –C 3 Ps –C 4 Ps –CAM Ps...
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Transcript of Ch. 2 Photosynthesis (Ps) and Light. C 4 Photosynthesis 3 patterns: –C 3 Ps –C 4 Ps –CAM Ps...
Ch. 2 Photosynthesis (Ps) and Light
C4 Photosynthesis• 3 patterns:
– C3 Ps
– C4 Ps
– CAM Ps
• Minimize FFF (fatal flaws of fotosynthesis)
C4 photosynthesis
C4 leaf anatomy• Kranz anatomy (“wreath:” German):
C4 pathway• Mesophyll fix CO2 New enzyme (PEP carboxylase)
C4 pathway• PEP carboxylase:
Why calledC4 Ps?
C4 pathway• BSC: Reaction reversed….• CO2 to• Pyruvate to
C shuttle!!
Calvin Cycle (Rubisco)
C4 pathway• C fixation & Ps
C4 pathway
• Advantages?
FFF?
Fatal Flaws of Fotosynthesis!
C4 advantages• Benefits:
– 1) PEP Carboxylase fix C
Photorespiration: A FFF!
C4 advantages• Benefits:
– 2) CO2 concentrated bundle sheath
C4 advantages• Benefits:
– 3) Less H20 loss.
Stoma
C4
Good sucker?
A FFF!
C4 advantages• Benefits:
– 4) Decrease Rubisco:– High NUE (nitrogen use efficiency):
Now:CAM
CAM photosynthesis• CAM:• Crassulaceae: • Acid: Leaves
Diamorpha smallii(Crassulaceae)
Leaf anatomy• Succulent
Leaf anatomy• Mesophyll• Cells large: • Vascular bundle sheath
CAM pathway• Separates C fixation & Ps
Separation in space: C4
CAM pathway• Night:
– Stomata open
– CO2 fixed:
Malic acid
CAM pathway• Acid stored• Leaf pH
Acid drop inskateboarding
CAM pathway• Day
– Stomata
– Reaction
– Ps: Calvin Cycle
CAM pathway• Separates C fixation and Ps
Night Day
CAM advantages• 1) PEP carboxylase fixes C:
photorespiration
CAM advantages• 2) Stomata open night. Less water loss!
CAM advantages• 3) Stomata closed day.
CAM variation• Dependence on CAM varies• Some: • CAM & succulence
Fig. 2.14More succulence,More CAM
Aeonium arboreum
CAM variation• Carbon cycling:
• Ex, Welwitschia mirabilis (Namib desert S. Africa)
• Gymnosperm: 2 leaves!
Some plants may be 1,000 yr old
Comparing C3, C4, CAM plants• Taxa: most plants
• C4 plants:
• Exs:• Some grasses: Sugar cane (Saccharum spp.)
Amaizing Facts*• Corn or maize (Zea mays)
*another cornyBoyd joke.....
Comparing C3, C4, CAM plants• Dicots:
– Kudzu (Pueraria montana)
Comparing C3, C4, CAM plants• Typical C4 plant habitat:
• In temperate areas: – winter/spring
– summer
Comparing C3, C4, CAM plants• % grass flora C4 in N. America
Fig. 2.18
Comparing C3, C4, CAM plants• CAM plants:
• Exs: many cacti (saguaro, cholla)
Saguaro “arms”
Comparing C3, C4, CAM plants• Exs: Agave species
– Economic use??
Comparing C3, C4, CAM plants• Exs: some Crassulaceae (Diamorpha smallii)
CAM and Epiphytes• Epiphytes:
– Abundant tropical rain forests
CAM and Epiphytes• Alabama• Spanish moss (Tillandsia
usneoides)• CAM plant:
Comparing C3, C4, CAM plants• Exs: many
(esp. epiphytic ones)
Comparing C3, C4, CAM plants• CAM plants:
Comparing C3, C4, CAM plants• Trait C3 C4 CAM
• Max. Ps rate
Fig. 2.12
Comparing C3, C4, CAM plants• Trait C3 C4 CAM
• Max. growth rate• (optimal conditions)
Comparing C3, C4, CAM plants• Trait C3 C4 CAM
• Optimum Ps temperature
Fig. 2.11