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Jan. 25 th , 2011 B4730/5730 Plant Physiological Ecology

Jan. 25 th , 2011 B4730/5730 Plant Physiological Ecology. Photosynthesis I. Examples of Energy Balance Using Eddy Covariance Techniques. Wilson et al. Ag. For. Met. 2002. Picea mariana ; Goulden et al. 1997. Baldocchi et al. 1997. Plants respond to environment with fluxes. Plant fluxes

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Jan. 25 th , 2011 B4730/5730 Plant Physiological Ecology

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  1. Jan. 25th, 2011B4730/5730Plant Physiological Ecology Photosynthesis I

  2. Examples of Energy Balance Using Eddy Covariance Techniques Wilson et al. Ag. For. Met. 2002

  3. Picea mariana; Goulden et al. 1997 Baldocchi et al. 1997

  4. Plants respond to environment with fluxes • Plant fluxes • Mass • Energy • Momentum • Soil Plant Atmosphere Continuum (SPAC) defines where fluxes occur • subcellular to global • Deriving flux equations; connecting anatomy • Photosynthesis • Transpiration • Importance of scale

  5. SPAC What other fluxes in SPAC besides water? http://www.fsl.orst.edu/~bond/phystalk/Ecohydrology/SPAC%20diagram.jpg

  6. Plant and Environmental Controls Over Photosynthesis • Within a given CA, plants control supply and demand for CO2 • full model of A requires both • Supply of CO2 determined by stomatal conductance (gs) • Balance transpiration (EL) and A • Environmental controls? • Demand for CO2 determined by mesophyll biochemistry • Limited by amount of RuBP, Rubsico, ATP, & NADPH • Farqhuar model with fluorescence combines all of above • Leaf vs. whole plant limitations

  7. Use of Environmental Response Curves in Photosynthesis • Response curves help propose and test physiological mechanisms in ecology • Light response reveals some light dependent mechanisms • Parameters: quantum yield, saturation, compensation, curvature • CO2 responses reveals some light independent mechanisms • Parameters: supply, demand, compensation, Rubisco, RuBP, CO2 and Phosphate • Multivariate controls on response curves

  8. C.m. shade C3, H.v. sun C3, Z.m. sun C4 BL blue light, RL red light Bukhov et al 1995 J. Photo. Chem. Bio.

  9. Pinus pinaster, Medlyn et al 2002 PCE

  10. States of Calvin Cycle Photosynthesis • State one-Rubsico limited • CO2 low • No Vcmax limitation • State two-RuBP regeneration limited • Light limited • Enzymes of Calvin cycle limited • Increases with increasing CO2 • State three-Triose Phosphate Use (TPU) • Photosynthesis at higher rate than capacity to use products • Not CO2 or O2 limited • Actual A rate is which of three states is limiting • Farqhuar et al (1980) model used to determine which one

  11. Sharkey et al. PCE 2007; incorporates newest material to Farquhar model

  12. Farquhar Model Overview • Five parameters from Farquhar model • VCmax - maximum carboxylation by Rubisco • J - rate of photosynthetic electron transport • TPU - triose phosphate use • Rd - day respiration • gm-mesophyll conductance • Parameters adjusted to 25 °C for comparison • c is scaling constant = 1 at 25 C), ΔHa enthalpy of activation, ΔHd enthalpy of deactivation, ΔS entropy, R is universal gas constant, T is temperature in K

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