Vegetatio

, Volume 104, Issue 1, pp 33–45

Analysing the responses of photosynthetic CO2 assimilation to long-term elevation of atmospheric CO2 concentration

  • S. P. Long
  • N. R. Baker
  • C. A. Raines
Methodology

DOI: 10.1007/BF00048143

Cite this article as:
Long, S.P., Baker, N.R. & Raines, C.A. Vegetatio (1993) 104: 33. doi:10.1007/BF00048143

Abstract

Understanding how photosynthetic capacity acclimatises when plants are grown in an atmosphere of rising CO2 concentrations will be vital to the development of mechanistic models of the response of plant productivity to global environmental change. A limitation to the study of acclimatisation is the small amount of material that may be destructively harvested from long-term studies of the effects of elevation of CO2 concentration. Technological developments in the measurement of gas exchange, fluorescence and absorption spectroscopy, coupled with theoretical developments in the interpretation of measured values now allow detailed analyses of limitations to photosynthesisin vivo. The use of leaf chambers with Ulbricht integrating spheres allows separation of change in the maximum efficiency of energy transduction in the assimilation of CO2 from changes in tissue absorptance. Analysis of the response of CO2 assimilation to intercellular CO2 concentration allows quantitative determination of the limitation imposed by stomata, carboxylation efficiency, and the rate of regeneration of ribulose 1:5 bisphosphate. Chlorophyll fluorescence provides a rapid method for detecting photoinhibition in heterogeneously illuminated leaves within canopies in the field. Modulated fluorescence and absorption spectroscopy allow parallel measurements of the efficiency of light utilisation in electron transport through photosystems I and IIin situ.

Keywords

Greenhouse effectChlorophyll fluorescenceRubisCQPhotosystem IIStomataQuantum efficiency

Abbreviations

A

net rate of CO2 uptke per unit leaf area (µmol m−2 s−1)

Asat

light-saturated A

ΔA820

change in absorptance of PSI on removal of illumination (OD)

c

CO2 concentration in air (µmol mol−1)

ca

c in the bulk air; ci, c in the intercellular spaces

ce

carboxylation efficiency (mol m−2 s−1)

E

transpiration per unit leaf area (mol m−2 s−1)

F

fluorescence emission of PSII (relative units)

Fm

maximal level of F

Fo

minimal level of F upon illumination when PSII is maximally oxidised

Fs

the steady-state F following the m peak

Fv

the difference between Fm and Fo

F'm

maximal F' generated after the m peak by addition of a saturating light pulse

F'o

the minimal level of F' after the m peak determined by re-oxidising PSII by far-red light

g1

leaf conductance to CO2 diffusion in the gas phase (mol m−2 s−1)

g'1

leaf conductance to water vapour diffusion in the gas phase (mol m−2 s−1)

kc and ko

the Michaelis constants for CO2 and O2, respectively, (µmol mol−1);

Jmax

the maximum rate of regeneration of rubP (µmol m−2 s−1)

l

stomatal limitation to CO2 uptake (dimensionless, 0–1)

LCP

light compensation point of photosynthesis (µmol m−2 s−1)

oi

the intercellular O2 concentration (mmol mol−1)

Pi

cytosol inorganic phosphate concentration

PSI

photosystem I

PSII

photosystem II

Q

photon flux (µmol m−2 s−1)

Qabs

Q absorbed by the leaf

rubisCO

ribulose 1:5 bisphosphate carboxylase/oxygenase; rubP, ribulose 1:5 bisphosphate; s, projected surface area of a leaf (m2)

Vc,max

is the maximum rate of carboxylation (µmol m−2 s−1)

Wc

the rubisCO limited rate of carboxylation (µmol m−2 s1)

Wj

the electron transport limited rate of regeneration of rubP (µmol m−2 s−1)

Wp

the inorganic phosphate limited rate of regeneration of rubP (µmol m−2 s−1)

α

absorptance of light (dimensionless, 0–1)

αa

α of standard black absorber α1, α of leaf

αs

α of integrating sphere walls

Γ, CO2

compensation point of photosynthesis (µmol mol−1)

τ

the specificity factor for rubisCO carboxylation (dimensionless)

θ,

convexity of the response of A to Q (dimensionless 0–1)

φ

the quantum yield of photosynthesis on an absorbed light basis (δA/δQabs; dimensionless)

φ

the quantum yield of photosynthesis on an incident light basis (δA/δQ; dimensionless)

φapp

the maximum φ

φm

the maximum φ

φm,app

the photochemical efficiency of PSII (dimensionless, 0–1)

φPSII,m

the maximum φ

Copyright information

© Kluwer Academic Publishers 1993

Authors and Affiliations

  • S. P. Long
    • 1
    • 2
  • N. R. Baker
    • 1
    • 2
  • C. A. Raines
    • 1
    • 2
  1. 1.Dept. of BiologyUniversity of EssexColchesterUK
  2. 2.Dept. of Applied SeienceBrookhaven Natl. Lab.UptonUSA