Tuesday, April 29, 1997 Lecture 9

DISCUSS ASSIGNMENT

• Paper 2 - due May 1
  • describe reinvestment strategies and give a specific example from photosynthesis
  • describe the results from the EXCEL spreadsheet on adaptation
  • describe your STELLA model for this process
  • give two examples from the literature on the process of adaptation (not the end point or optimization)
• I'll review your outline if submitted by Friday

• Specific learning objectives for EXCEL and STELLA
  • be able to manipulate the light and cell components in our first EXCEL model
  • be able to write the two simplest strategies into our EXCEL adaptation model
    • percent of the new production going into each component
    • all or nothing adaptation based on if - then construct
  • be able to graph non-contiguous groups of cells
  • be able to make a simple exponential growth model in STELLA and graph the results
  • be able to make a reinvestment model in STELLA that the reinvestment depend on which process is limiting.
• schedule help

• Basic
  • Construct the model as shown in the handout (and below).
  • Show how the model adapts to changes in light for example light=100, 1000 and 20 and describe the behavior of the major stocks.
  • What is the sensitivity to different starting components (say 5 and 5 instead of 7 and 3)?
• More advanced
  • How do your results with STELLA compare to those with EXCEL?
  • how does the model react to the light regimes that we used with the EXCEL model? (Make the light function into a graph of time).
  • How does the choice of time step size (DT under the time specs dialog box) change the results?
  • What changes might you make to this model?

Diagram of the STELLA adaptation model

Equations for the STELLA adaptation model

carbon_production(t) = carbon_production(t - dt) + (enz_rxn - reinvest_Pmemb - reinvest_Penz) * dt
INIT carbon_production = 0

INFLOWS:
enz_rxn = penz
OUTFLOWS:
reinvest_Pmemb = if indicator = 1 then carbon_production else 0
reinvest_Penz = if indicator=0 then carbon_production else 0

NADPH(t) = NADPH(t - dt) + (light_rxn - enz_rxn) * dt
INIT NADPH = 0

INFLOWS:
light_rxn = pmemb*light/(light+100)
OUTFLOWS:
enz_rxn = penz
penz(t) = penz(t - dt) + (reinvest_Penz) * dt
INIT penz = 3

INFLOWS:
reinvest_Penz = if indicator=0 then carbon_production else 0

pmemb(t) = pmemb(t - dt) + (reinvest_Pmemb) * dt
INIT pmemb = 7

INFLOWS:
reinvest_Pmemb = if indicator = 1 then carbon_production else 0
indicator = if light_rxn <= enz_rxn then 1 else 0
total_carbon = penz+pmemb+carbon_production
light = GRAPH(time)
(0.00, 100), (1.00, 100), (2.00, 100), (3.00, 99.0), (4.00, 200), (5.00, 200), (6.00, 200), (7.00, 199), (8.00, 49.0), (9.00, 48.0), (10.0, 48.0), (11.0, 48.0), (12.0, 51.0)