Abstract
Abstract As global carbon dioxide concentrations rise, we need to understand the combination of direct effects of this gas and the anticipated effects of climate change, including drought, on physiology and growth of all crops. Effects of CO 2 on plants begin at the leaf level; our objectives, therefore, were to determine interrelationships among factors governing gas exchange responses of soybean [ Glycine max (L.) Merr.] leaves to elevated CO 2 and water stress. Photosynthetic CO 2 assimilation and transpiration rates were measured in cuvettes on leaflets of soybean (cv. Bragg) grown in controlled‐environment chambers at 330 and 660 μmol CO 2 mol −1 air. Leaflets at high CO 2 , either water‐stressed or wellwatered, had higher photosynthetic and lower transpiration rates, and therefore higher water‐use efficiencies (WUE), than those at control CO 2 levels. As irrigation was withheld during an ll‐d period, WUE decreased about 30 to 50% with respect to the well‐watered treatments. Midday leaf temperature and leaf‐to‐air vapor pressure gradient levels increased as the water stress progressed. For water stress treatments, midday leaf conductance ( G tw ) was generally higher and residual internal conductance ( G r ) was generally lower in low than in high CO 2 . Ratios of midday G r / G tc were nearly constant throughout the period in both the stressed and the well‐watered treatments. The ratios of intercellular C i , to ambient C a , CO 2 concentration (i.e., C i / C a ) during the water stress period remained similar to the respective nonstressed treatments within each CO 2 level. These findings support the concept that leaf conductances are governed by CO 2 assimilation rates under water‐stressed as well as unstressed conditions.
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Claims 11
Claim · model-written summary
High CO 2 increased soybean leaf photosynthetic rates relative to control CO 2.
- Taxon
- soybean
Glycine maxe1 - Material
- cv. Bragge1
- Treatment
- high CO 2e0
- Outcome
- photosynthetice0
- Direction
- highere0
- Comparator
- control CO 2 levelse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Leaflets at high CO 2 , either water‐stressed or wellwatered, had higher photosynthetic and lower transpiration rates, and therefore higher water‐use efficiencies (WUE), than those at control CO 2 levels”
e1“soybean (cv. Bragg)”
Claim · model-written summary
High CO 2 reduced transpiration rates relative to control CO 2.
- Taxon
- soybeanGlycine maxe1
- Material
- cv. Bragge1
- Treatment
- high CO 2e0
- Outcome
- transpiration ratese0
- Direction
- lowere0
- Comparator
- control CO 2 levelse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Leaflets at high CO 2 , either water‐stressed or wellwatered, had higher photosynthetic and lower transpiration rates, and therefore higher water‐use efficiencies (WUE), than those at control CO 2 levels”
e1“soybean (cv. Bragg)”
Claim · model-written summary
High CO 2 increased water use efficiency relative to control CO 2.
- Taxon
- soybeanGlycine maxe1
- Treatment
- high CO 2e0
- Outcome
- water‐use efficiencies (WUE)e0
- Direction
- highere0
- Comparator
- control CO 2 levelse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Leaflets at high CO 2 , either water‐stressed or wellwatered, had higher photosynthetic and lower transpiration rates, and therefore higher water‐use efficiencies (WUE), than those at control CO 2 levels”
e1“soybean (cv. Bragg)”
Claim · model-written summary
Withholding irrigation decreased WUE about 30 to 50% relative to well watered treatments.
- Taxon
- soybeanGlycine maxe1
- Treatment
- irrigation was withhelde0
- Outcome
- WUEe0
- Direction
- decreasede0
- Value
- 30 to 50%e0
- Comparator
- well‐watered treatmentse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“As irrigation was withheld during an ll‐d period, WUE decreased about 30 to 50% with respect to the well‐watered treatments”
e1“soybean (cv. Bragg)”
Claim · model-written summary
Midday leaf temperature increased as water stress progressed.
- Taxon
- soybeanGlycine maxe1
- Treatment
- water stresse0
- Outcome
- Midday leaf temperaturee0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Midday leaf temperature and leaf‐to‐air vapor pressure gradient levels increased as the water stress progressed”
e1“soybean (cv. Bragg)”
Claim · model-written summary
Leaf to air vapor pressure gradient increased as water stress progressed.
- Taxon
- soybeanGlycine maxe1
- Treatment
- water stresse0
- Outcome
- leaf‐to‐air vapor pressure gradient levelse0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Midday leaf temperature and leaf‐to‐air vapor pressure gradient levels increased as the water stress progressed”
e1“soybean (cv. Bragg)”
Claim · model-written summary
Under water stress, midday leaf conductance was generally higher at low than high CO 2.
- Taxon
- soybeanGlycine maxe1
- Treatment
- lowe0
- Outcome
- midday leaf conductance ( G tw )e0
- Direction
- highere0
- Qualifier
- water stress treatmentse0
- Comparator
- high CO 2e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“For water stress treatments, midday leaf conductance ( G tw ) was generally higher and residual internal conductance ( G r ) was generally lower in low than in high CO 2”
e1“soybean (cv. Bragg)”
Claim · model-written summary
Under water stress, residual internal conductance was generally lower at low than high CO 2.
- Taxon
- soybeanGlycine maxe1
- Treatment
- lowe0
- Outcome
- residual internal conductance ( G r )e0
- Direction
- lowere0
- Qualifier
- water stress treatmentse0
- Comparator
- high CO 2e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“For water stress treatments, midday leaf conductance ( G tw ) was generally higher and residual internal conductance ( G r ) was generally lower in low than in high CO 2”
e1“soybean (cv. Bragg)”
Claim · model-written summary
Midday conductance ratios remained nearly constant in stressed and well watered treatments.
- Taxon
- soybeanGlycine maxe1
- Outcome
- Ratios of midday G r / G tce0
- Direction
- nearly constante0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Ratios of midday G r / G tc were nearly constant throughout the period in both the stressed and the well‐watered treatments”
e1“soybean (cv. Bragg)”
Claim · model-written summary
C i / C a ratios during water stress remained similar to nonstressed treatments at each CO 2 level.
- Taxon
- soybeanGlycine maxe1
- Treatment
- water stress periode0
- Outcome
- C i / C ae0
- Direction
- remained similare0
- Comparator
- nonstressed treatmentse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“C i / C a ) during the water stress period remained similar to the respective nonstressed treatments within each CO 2 level”
e1“soybean (cv. Bragg)”
Claim · model-written summary
The authors interpreted leaf conductances as governed by CO 2 assimilation rates under stressed and unstressed conditions.
- Taxon
- soybeanGlycine maxe1
- Outcome
- leaf conductancese0
- Qualifier
- CO 2 assimilation ratese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“leaf conductances are governed by CO 2 assimilation rates under water‐stressed as well as unstressed conditions”
e1“soybean (cv. Bragg)”
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See all 69 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.