Feb. 8th, 2011 B4730/5730 Plant Physiological Ecology Respiration II

Acclimation of Respiration Respiration rates Increase during acclimation to cold Decrease during acclimation to heat Biochemical regulation counteracts the tendencies of the physiological rates Depend on tissue/organ status Quantitative description of respiration Arrhenius, activation energy Q10 R=Roexp[(lnQ10/10)·T] Q10 varies from 1.0 to 3 reference respiration and Q10 still not fully predictable

Pinus radiata Ryan et al. Tree Phys. 1996 Eucalyptus regnans Ryan et al Eco Mono 2004

Pinus radiata; Kruse et al New Phyt 2008

Chamaecyparis obtusa, Hagihara and Hozumi 1991 Rook 1969

California grass and shrubs; Carbone et al JGR Bio 2008

Picea mariana fen (2006 warmer and drier); Cai et al PCE 2010

Respiration components 60% of maintenance R is from protein synthesis/repair, membrane repair, and ion gradients Growth respiration includes carbon cost of synthesizing tissue from sugars and minerals Theoretical analysis of biochemical pathways Elemental analysis Heat of Combustion ~25% of carbon allocation? N uptake costs (transport) are usually much higher than phosphorous and other nutrients Few estimates of total carbon costs, 10-60% (Ryan 1991) Uses reductant (e.g. NADH reductase) from mitochondria

Lavingne et al New Phyt 2004

Lavingne et al New Phyt 2004

Intro to Stable Isotopes Origin of Atoms and Elements Composition of an atom (“nuclide”) is described by the number of protons and neutrons in the nucleus: A = Z + N where A is mass number, Z is number of protons, N is number of neutrons Only 264 of 1700 known nuclides are stable Most of these have even Z and even N; even Z and odd N are less common; odd Z and odd N are rare

Origin of Atoms and Elements (5) Most relevant for ecological applications: Element Isotope Abundance (%) Hydrogen 1H 99.985 2H 0.015 Carbon 12C 98.89 13C 1.11 14C <10-10 Nitrogen 14N 99.63 15N 0.37 Oxygen 16O 99.759 17O 0.037 18O 0.204

Terms and Definitions I Stable isotopes are rare in abundance but can be measured very accurately by isotope ratio mass spectrometers (IRMS) (or lasers now), in which the ratio of heavy to light isotopes in a samples is compared with the ratio in a standard Use delta notation to express these values conveniently: d13C = ([(13C/12C)sample/(13C/12C)standard] - 1) 1000 Delta values are expressed in parts per thousand, or “per mil” (‰) International standards are used so all delta values are intercomparable

Terms and Definitions (and a little jargon) Standards: PDB limestone for C, Standard Mean Ocean Water (SMOW) for H and O, atmospheric N2 for N If a sample has more of the heavy isotope than the standard (or than another substance) it is “enriched” or “heavier” and if it has less it is “depleted” or “lighter” Examples: d13C of PDB = 0‰ d13C of atmospheric CO2 = -8‰ d13C of C3 plants is around -25‰ IF Pee Dee Belemnite (PDB) has 13C/12C = 0.011237, what is the 13C/12C ratio of CO2 in air?