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A computer‐operated routine of gas exchange and optical measurements to diagnose photosynthetic apparatus in leaves
Author(s) -
Laisk A.,
Oja V.,
Rasulov B.,
Rämma H.,
Eichelmann H.,
Kasparova I.,
Pettai H.,
Padu E.,
Vapaavuori E.
Publication year - 2002
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1046/j.1365-3040.2002.00873.x
Subject(s) - photosynthesis , p700 , analytical chemistry (journal) , plastoquinone , chemistry , botany , photosystem ii , materials science , photosystem i , biology , chloroplast , environmental chemistry , biochemistry , thylakoid , gene
Photosynthesis is a complex process whose rate is affected by many biochemical and biophysical factors. Fortunately, it is possible to determine, or at least estimate, many of the most important parameters using a combination of optical methods and gas transient analyses. We describe here a computer‐operated routine that has been developed to make detailed assessments of photosynthesis at a comprehensive level. The routine comprised the following measurements: steady‐state light and CO 2 response curves of net CO 2 assimilation at 21 and 2 kPa O 2 ; transients from limiting to different saturating CO 2 concentrations at 2 kPa O 2 ; post‐illumination CO 2 fixation transient; dark–light induction of O 2 evolution; O 2 yield from one saturating single‐turnover flash; chlorophyll fluorescence F 0 , F s and F m during the light and CO 2 response curves; leaf transmission at 820 nm (P700 + ) during the light and CO 2 response curves; post‐illumination re‐reduction time of P700 + . The routine was executed on a two‐channel fast‐response gas exchange measurement system (A. Laisk and V. Oja: Dynamic Gas Exchange of Leaf Photosynthesis. CSIRO, Canberra, Australia). Thirty‐six intrinsic characteristics of the photosynthetic machinery were derived, including quantum yield of CO 2 fixation ( Y CO2 ), time constant of P700 re‐reduction ( τ ′), relative optical cross‐sections of PSII and PSI antennae ( a II , a I ), PSII and PSI density per leaf area unit, plastoquinone pool, total mesophyll resistance, mesophyll diffusion resistance, V m , K m (CO 2 ) and CO 2 /O 2 specificity of Rubisco, RuBP pool at CO 2 limitation (assimilatory charge). An example of the routine and calculations are shown for one leaf and data are presented for leaves of 8‐year‐old‐trees of two birch clones growing in Suonenjoki Forest Research Station, Finland, during summer 2000. Parameters Y CO2 , basic τ ′, a II , a I , K m (CO 2 ) and K s varied little in different leaves [relative standard deviation (RSD) < 7%], other parameters scattered widely (RSD typically 10–40%). It is concluded that the little scattered parameters are determined by basic physico‐chemical properties of the photosynthetic machinery whereas the widely scattered parameters are adjusting to growth conditions. The proposed non‐destructive routine is suitable for diagnosing the photosynthetic machinery of leaves and may be applied in plant ecophysiology and in genetic engineering of plants.