Abstract
Two herbaceous perennials, alfalfa ( Medicago sativa L. cv. Arc) and orchard grass ( Dactylus glomerata L. cv. Potomac), were grown at ambient (367 μmol mol −1 ) and elevated (729 μmol mol −1 ) CO 2 concentrations at constant temperatures of 15, 20, 25 and 30°C in order to examine direct and indirect changes in nighttime CO 2 efflux rate (respiration) of single leaves. Direct (biochemical) effects of CO 2 on nighttime respiration were determined for each growth condition by brief (<30 min) exposure to each CO 2 concentration. If no direct inhibition of respiration was observed, then long‐term reductions in CO 2 efflux between CO 2 treatments were presumed to be due to indirect inhibition, probably related to long‐term changes in leaf composition. By this criterion, indirect effects of CO 2 on leaf respiration were observed at 15 and 20°C for M. sativa on a weight basis, but not on a leaf area or protein basis. Direct effects however, were observed at 15, 20 and 25°C in D. glomerata ; therefore the observed reductions in respiration for leaves grown and measured at elevated relative to ambient CO 2 concentrations could not be distinguished as indirect inhibition. No inhibition of respiration at elevated CO 2 was observed at the highest growth temperature (30°C) in either species. CO 2 efflux increased with measurement and growth temperature for M. sativa at both CO 2 concentrations; however, CO 2 efflux in D. glomerata showed complete acclimation to growth temperature. Stimulation of leaf area and weight by elevated CO 2 levels declined with growth temperature in both species. Data from the present study suggest that both direct and indirect inhibition of respiration are possible with future increases in atmospheric CO 2 , and that the degree of each type of respiratory inhibition is a function of growth temperature.
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Claims 6
Claim · model-written summary
Elevated CO2 indirectly inhibited M. sativa respiration at 15 and 20°C on a weight basis.
- Taxon
- M. sativa
Medicago sativae0 - Treatment
- CO 2e0
- Outcome
- leaf respiratione0
- Direction
- indirect effectse0
- Qualifier
- 15 and 20°Ce0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“indirect effects of CO 2 on leaf respiration were observed at 15 and 20°C for M. sativa on a weight basis, but not on a leaf area or protein basis.”
Claim · model-written summary
Direct CO2 effects on D. glomerata respiration occurred at 15, 20, and 25°C.
Not reportedTreatmentComparatorDirection
Verbatim
e0“Direct effects however, were observed at 15, 20 and 25°C in D. glomerata”
Claim · model-written summary
Neither species showed respiratory inhibition at elevated CO2 and 30°C.
Not reportedTaxonComparator
Verbatim
e0“No inhibition of respiration at elevated CO 2 was observed at the highest growth temperature (30°C) in either species.”
Claim · model-written summary
M. sativa CO2 efflux increased with measurement and growth temperature.
- Taxon
- M. sativaMedicago sativae0
- Treatment
- measurement and growth temperaturee0
- Outcome
- CO 2 effluxe0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“CO 2 efflux increased with measurement and growth temperature for M. sativa at both CO 2 concentrations”
Claim · model-written summary
D. glomerata CO2 efflux acclimated completely to growth temperature.
Verbatim
e0“CO 2 efflux in D. glomerata showed complete acclimation to growth temperature.”
Claim · model-written summary
Elevated CO2 stimulation of leaf area and weight declined with growth temperature in both species.
- Treatment
- elevated CO 2 levelse0
- Outcome
- leaf area and weighte0
- Direction
- declinede0
- Qualifier
- growth temperaturee0
Not reportedTaxonComparator
Verbatim
e0“Stimulation of leaf area and weight by elevated CO 2 levels declined with growth temperature in both species.”
The same questions in other papers
co2 · growth · Medicago sativa (alfalfa)Positive and negative results
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See all 20 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.