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 called C4 Ps?

C4 pathway BSC: Reaction reversed…. CO2 to Pyruvate to C shuttle!! Calvin Cycle (Rubisco) C shuttle!!

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 A FFF! Benefits: 3) Less H20 loss. Stoma C4 Good sucker?

C4 advantages Benefits: 4) Decrease Rubisco: High NUE (nitrogen use efficiency): Now: CAM

CAM photosynthesis CAM: Crassulaceae: Acid: Leaves Diamorpha smallii

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 in skateboarding

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 Aeonium arboreum Fig. 2.14 More succulence, More CAM

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 corny Boyd 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 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

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