Abstract
Gas exchange by stems is dominated by respiratory CO2 emission, but photosynthetic CO2 uptake might also occur in stem bark. We show that light-dependent CO2 uptake was present and often exceeded CO2 release by respiration in illuminated current-year peach (Prunus persica L.) stems. Respiration of peach stems, as detected by 12CO2 release into air in which the natural concentration of 12CO2 was replaced with 13CO2, was lower in the light than in the dark, but this accounted for only a fraction of the observed total CO2 uptake by illuminated stems. Stem photosynthesis was saturated at low light and was negatively affected by elevated assay temperatures (30°C), especially when combined with light intensities above saturation. An inefficient mechanism of heat dissipation by transpiration in stomata-free stems might help explain this effect. Photosynthesis was rapidly stimulated and the electron transport rate was reduced when photorespiration was suppressed by exposure to low (2 kPa) oxygen. The time-course of these changes was closely associated with a transient burst of CO2 uptake concurrent with a reduced inhibition of fluorescence yield. Photosynthesis was also stimulated by exposure to elevated (twice ambient) CO2 concentration. These combined measurements of gas exchange and fluorescence suggested that (a) photorespiration may also be active in the bark of peach stems, (b) O2 and CO2 concentrations in the bark of peach stems may be similar to ambient concentrations, (c) a large amount of electron transport unrelated to photosynthesis and photorespiration may also be present in peach stems, and (d) stem photosynthesis may be enhanced under future atmospheric conditions.
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Claims 12
Claim · model-written summary
Light-dependent CO2 uptake was present in illuminated peach stems and often exceeded respiratory CO2 release.
- Taxon
- peach
Prunus persicae0 - Outcome
- CO2 uptakee1
- Qualifier
- exceeded CO2 release by respiratione1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Respiration of peach stems”
e1“CO2 uptake was present and often exceeded CO2 release by respiration”
Claim · model-written summary
Respiration of peach stems was lower in the light than in the dark, but accounted for only a fraction of the total CO2 uptake.
- Taxon
- peachPrunus persicae0
- Treatment
- lighte2
- Outcome
- Respiratione0
- Direction
- lowere2
- Qualifier
- accounted for only a fraction of the observed total CO2 uptakee3
- Comparator
- darke2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Respiration of peach stems”
e2“was lower in the light than in the dark”
e3“accounted for only a fraction of the observed total CO2 uptake”
Claim · model-written summary
Stem photosynthesis of peach was saturated at low light.
- Taxon
- peachPrunus persicae0
- Outcome
- Stem photosynthesise4
- Qualifier
- saturated at low lighte4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Respiration of peach stems”
e4“Stem photosynthesis was saturated at low light”
Claim · model-written summary
Elevated assay temperature negatively affected stem photosynthesis of peach, especially at light intensities above saturation.
- Taxon
- peachPrunus persicae0
- Treatment
- elevated assay temperaturese5
- Outcome
- Stem photosynthesise4
- Direction
- negatively affectede5
- Qualifier
- especially when combined with light intensities above saturatione6
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Respiration of peach stems”
e4“Stem photosynthesis was saturated at low light”
e5“was negatively affected by elevated assay temperatures”
e6“especially when combined with light intensities above saturation”
Claim · model-written summary
Exposure to low (2 kPa) oxygen rapidly stimulated photosynthesis of peach stems by suppressing photorespiration.
- Taxon
- peachPrunus persicae0
- Treatment
- exposure to low (2 kPa) oxygene1
- Outcome
- Photosynthesise7
- Direction
- stimulatede7
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Respiration of peach stems”
e7“Photosynthesis was rapidly stimulated”
e1“when photorespiration was suppressed by exposure to low (2 kPa) oxygen”
Claim · model-written summary
Exposure to low (2 kPa) oxygen reduced the electron transport rate of peach stems.
- Taxon
- peachPrunus persicae0
- Treatment
- exposure to low (2 kPa) oxygene1
- Outcome
- electron transport ratee2
- Direction
- reducede2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Respiration of peach stems”
e1“when photorespiration was suppressed by exposure to low (2 kPa) oxygen”
e2“the electron transport rate was reduced”
Claim · model-written summary
The time course of the low-oxygen effect was associated with a transient burst of CO2 uptake in peach stems.
- Taxon
- peachPrunus persicae0
- Treatment
- low (2 kPa) oxygene1
- Outcome
- transient burst of CO2 uptakee2
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Respiration of peach stems”
e1“when photorespiration was suppressed by exposure to low (2 kPa) oxygen”
e2“was closely associated with a transient burst of CO2 uptake”
Claim · model-written summary
Elevated (twice ambient) CO2 stimulated photosynthesis of peach stems.
- Taxon
- peachPrunus persicae0
- Treatment
- elevated (twice ambient) CO2 concentratione1
- Outcome
- Photosynthesise1
- Direction
- stimulatede1
- Comparator
- ambiente1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Respiration of peach stems”
e1“Photosynthesis was also stimulated by exposure to elevated (twice ambient) CO2 concentration”
Claim · model-written summary
Photorespiration may also be active in the bark of peach stems.
- Taxon
- peachPrunus persicae0
- Organ / stage
- barke0
- Outcome
- photorespiratione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“photorespiration may also be active in the bark of peach stems”
Claim · model-written summary
O2 and CO2 concentrations in the bark of peach stems may be similar to ambient concentrations.
- Taxon
- peachPrunus persicae0
- Outcome
- O2 and CO2 concentrationse0
- Qualifier
- similar to ambient concentrationse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“O2 and CO2 concentrations in the bark of peach stems may be similar to ambient concentrations”
Claim · model-written summary
A large amount of electron transport unrelated to photosynthesis and photorespiration may be present in peach stems.
- Taxon
- peachPrunus persicae0
- Outcome
- electron transporte0
- Qualifier
- unrelated to photosynthesis and photorespiratione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a large amount of electron transport unrelated to photosynthesis and photorespiration may also be present in peach stems”
Claim · model-written summary
Stem photosynthesis of peach may be enhanced under future atmospheric conditions.
- Taxon
- peachPrunus persicae0
- Treatment
- future atmospheric conditionse1
- Outcome
- stem photosynthesise1
- Direction
- enhancede1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Respiration of peach stems”
e1“stem photosynthesis may be enhanced under future atmospheric conditions”
The same questions in other papers
co2 · physiology: photosynthesis · Prunus persica (peach)Results agree
6 papers in the same direction as this paper
- positive
- positive
- positive
3 papers more in this group
See all 7 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.