jan. 25 th, 2011 b4730/5730 plant physiological ecology photosynthesis i
DESCRIPTION
Baldocchi et al Picea mariana; Goulden et al. 1997TRANSCRIPT
Jan. 25th, 2011B4730/5730
Plant Physiological Ecology
Photosynthesis I
Wilson et al. Ag. For. Met. 2002
Examples of Energy Balance Using Eddy Covariance Techniques
Baldocchi et al. 1997
Picea mariana; Goulden et al. 1997
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
SPAC
http://www.fsl.orst.edu/~bond/phystalk/Ecohydrology/SPAC%20diagram.jpg
What other fluxes in SPACbesides water?
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
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
C.m. shade C3, H.v. sun C3, Z.m. sun C4BL blue light, RL red lightBukhov et al 1995 J. Photo. Chem. Bio.
Pinus pinaster, Medlyn et al 2002 PCE
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
Sharkey et al. PCE 2007; incorporates newest material to Farquhar model
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
TRH
TS
TRH
c
d
a
e
eParameter
1