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Dynamic changes of canopy‐scale mesophyll conductance to CO 2 diffusion of sunflower as affected by CO 2 concentration and abscisic acid
Author(s) -
SCHÄUFELE RUDI,
SANTRUCEK JIRI,
SCHNYDER HANS
Publication year - 2011
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 - 10.1111/j.1365-3040.2010.02230.x
Subject(s) - abscisic acid , helianthus annuus , sunflower , canopy , chemistry , stomatal conductance , diffusion , isotopes of carbon , respiration , botany , horticulture , analytical chemistry (journal) , photosynthesis , biology , environmental chemistry , biochemistry , physics , total organic carbon , gene , thermodynamics
Leaf‐level measurements have shown that mesophyll conductance ( g m ) can vary rapidly in response to CO 2 and other environmental factors, but similar studies at the canopy‐scale are missing. Here, we report the effect of short‐term variation of CO 2 concentration on canopy‐scale g m and other CO 2 exchange parameters of sunflower ( Helianthus annuus L.) stands in the presence and absence of abscisic acid (ABA) in their nutrient solution. g m was estimated from gas exchange and on‐line carbon isotope discrimination (Δ obs ) in a 13 CO 2 / 12 CO 2 gas exchange mesocosm. The isotopic contribution of (photo)respiration to stand‐scale Δ obs was determined with the experimental approach of Tcherkez et al . Without ABA, short‐term exposures to different CO 2 concentrations ( C a 100 to 900 µ mol mol −1 ) had little effect on canopy‐scale g m . But, addition of ABA strongly altered the CO 2 ‐response: g m was high (approx. 0.5 mol CO 2 m −2 s −1 ) at C a < 200 µ mol mol −1 and decreased to <0.1 mol CO 2 m −2 s −1 at C a >400 µ mol mol −1 . In the absence of ABA, the contribution of (photo)respiration to stand‐scale Δ obs was high at low C a (7.2‰) and decreased to <2‰ at C a > 400 µ mol mol −1 . Treatment with ABA halved this effect at all C a .