• Field defined:  study of mechanisms that allow organisms to respond to their environment.
• Light & Plant Life

A.  all production except for chemosynthetic bacteria is due to autotrophic ìself-feedersî

B.  quality (spectral composition) & quantity(amount of energy) of light change with depth

• 1.  photoacclimation through pigment production
• 2.  changes in photosynthetic rates: sun vs. shade responses
• 3.  reorientation of chloroplasts
• 4.  phototactic & phototrophic responses
• 5.  day length timing of reproduction
• 6.  moving chloroplasts into epidermis: seagrasses
• 7.  thickness of mangrove upper leaves
• 8.  xeromorphy:  adaptation to H2O deficiencies

• 1.  Pigment Structure (Recognize structures!)
• a.  chlorophyll (a, b, c)
• b.  carotenoid (b carotene, siphonoxanthin, fucoxanthin)
• c.  phycobilins (phycoerythrin, phycocyanin)
• 2.  Structure of photosynthetic membrane
• 3.  Process of photosynthesis
• 4.  Action Spectra Vs. Absorption Spectra
• 5.  Phylogenetic chromatic adaption?
• 6.  Intensity adaptation by increasing total pigments?

4.  Graphic: Dawes Figure 4.1, Chlorophyll a & b
5. Graphic:   AbsorptionSpectra forChlorophylls a, b & c in Acetone From Falkowski & Raven, 1997.  Note red and blue peaks.

6.  Graphic:  Dawes Figure 4.3.  Phycobilins

• Component of major chromophores in Cyanobacteria and Rhodophyta
• No associated metal
• Absorption: blue-green, green,  yellow or orange light

8.  Graphic:  Dawes Figure 4.4.  Actionvs.AbsorptionSpectra

9.  Graphic: Dawes Figure 4.2.  Carotenoids

10.  Graphic:  a photosystem consists of an antenna and a reaction center.

11.  Graphic:  membrane bound components of a photosynthetic electron transport system in the thylakoid.

12.  Molecular Components of the Photosystems

• Proteins - PSII
• Cytochrome b559
• D1/D2 complex
• Water splitting complex with 4 Mn atoms
• Yz protein
• Pheophytin
• QA = quinone A
• Qb = quinone B
• Fe non-heme protein
• Proteins - PSI
• Ao, A1 = ETS component
• FeSx = iron sulfur cluster
• PCy = plastocyanin
• Cyt c6 = cytochrome c6
• Fd = ferredoxin
• Rx center chlorophylls (ID by absorption peak of isolated reaction center chlorophyll)
• PSII - P680
• PSI - P700

13.  Graphic: PSI organization. From Falkowski & Raven, 1997

• P700 = chla
• A1, A0 = large chlorophyll binding protein
• FeSx = iron sulfur cluster
• Fd = ferredoxin

15.  Graphic:  ATPase. From Falkowski & Raven, 1997

16.  Repeat graphic of molecular components of the photosynthetic membrane.

17.  Graphic:  Z-Scheme. Photosynthetic electron transport from Falkowski & Raven, 1997.

18.  How do marine plants protect from UV?

• 1.  UV- absorbing compounds: Gracilaria chilensis makes more if exposed to UV
• 2.  Ulva decreases growth, increase UV = decrease Ulva
• 3.  UV damages photosynthetic apparatus, blue-light exposure helps plant recover.
• 4.  Problems with decreased O3?

A.  General Model
B.  Changing # of traps, fixed antenna size
C.  Fixed # of traps, changing antenna size

• 1.  growth: photomorphogenic & phototropic  (phytochrome:  red/far red switch)
• 2.  development:  photoperiodic
• a.  germination
• b.  growing toward light in a shaded situation
• 3.  types of responses to day length
• a.  short-day plants: respond to photoperiods less than a critical day length
• ex.  Monostroma grevillei:  daylength determines life-history stage
• b.  long-day:  respond to photoperiod more than a critical day length
• c.  day-neutral:  photoperiod not critical

• 1.  diffusion in water 104 X slower than air
• 2.  boundary layer restricts further
• 3.  some seaweeds use HCO3- via carbonic anhydrase
• 4.  primary photosynthetic pathway of CO2 fixation is C3 pathway (Calvin cycle)
• a.  enzyme involved = RuBisCO, most abundant protein on the earth!!!!!!! =
• ribose-1,5-bisphosphate carboxylase oxygenase
• b.  C3 because 1-5C molecule + CO2 = 2-3C backbones=> eventually becomes 6C (glucose).

• 4 large subunits dimers arranged around a 4-fold axis to make core
• Clusters of 4 small subunits bind at each end
• Active sites for the enzyme are contained in the large subunits
• AS shown on left front dimer

24.  Graphic:  Complete Calvin-Bensen Cycle, from Falkowski & Raven, 1997

25.  Photorespiration:  net loss of fixed C => bad deal for the plant.

• 1.  Why?  RuBisCO can fix O2 as well as CO2, but donít get sugar as a result
• 2.  Some monocots solve this problem via the C4 pathway and an enzyme called PEPck, or phosphoenol pyruvate carboxylase.
•    a.  grasses isolate the RuBisCO into internal cells
•    b.  PEPck resides in outermost photosynthetic cells, grabs CO2 into a C4 compound
•    c.  the C4 compound is shuttled into an internal cell within the leaf where CO2 is pulled off and fed into the C3 pathway.
•    d.  works best in warm, high light environments, where there is plenty of sunlight energy:  C4 pathway is energetically expensive

27.  Graphic:  Formula 4-2.  Photorespiration