Abstract
Bunce, J. A. 1987. In-phase cycling of photosynthesis and conductance at saturating carbon dioxide pressure induced by increases in water vapour pressure deficit.—J. exp. Bot. 38: 1413–1420. The leaf to air water vapour deficit was increased suddenly from about 1·0 to 2·5 IcPa for single leaves of soybean (Glycine max L. Merr.) plants held at 30 °C, 2·0 mmol m −2 s−1 photosynthetic photon flux density (PPFD) and carbon dioxide pressures saturating to photosynthesis. After a lag of about 10 min, photosynthetic rate and stomatal conductance to water vapour began to decrease, and then cycled in phase with each other. The period of the cydes was about 20 min. During these cycles the substomatal carbon dioxide pressure was constant in the majority of leaves examined, and was always above saturation for photosynthesis. Epidermal impressions showed that most stomata changed in aperture during the cycles, and that very few were ever fully closed. Water potential measured on excised discs changed by at most 0·1 MPa from the minima to the maxima in transpiration rate. In contrast, for leaves of sunflower (Helianthus animus L.) grown at low PPFD, the increase in VPD led to leaf wilting and decreased photosynthesis, followed by recovery of turgor and photosynthesis as stomatal conductance began to decrease. In these leaves photosynthesis and conductance then cycled approximately 180° out of phase. It is suggested that in soybeans decreased leaf conductance induced by high VPD provided a signal which decreased the rate of photosynthesis at carbon dioxide saturation by a mechanism that was not related to a water deficit in the mesophyll.
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Claims 11
Claim · model-written summary
A sudden increase in leaf-to-air vapour deficit made soybean photosynthetic rate and stomatal conductance decrease after a lag of about 10 min
- Taxon
- soybean
Glycine maxe1 - Treatment
- increased suddenly from about 1·0 to 2·5 IcPae1
- Outcome
- photosynthetic rate and stomatal conductancee2
- Direction
- decreasee2
- Qualifier
- after a lag of about 10 mine2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“The leaf to air water vapour deficit was increased suddenly from about 1·0 to 2·5 IcPa for single leaves of soybean (Glycine max L. Merr.) plants held at 30 °C”
e2“After a lag of about 10 min, photosynthetic rate and stomatal conductance to water vapour began to decrease, and then cycled in phase with each other”
Claim · model-written summary
Soybean photosynthetic rate and stomatal conductance cycled in phase with each other
- Taxon
- soybeanGlycine maxe1
- Outcome
- cycled in phase with each othere2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“for single leaves of soybean (Glycine max L. Merr.) plants held at 30 °C”
e2“then cycled in phase with each other”
Claim · model-written summary
The soybean cycles had a period of about 20 min
- Taxon
- soybeanGlycine maxe1
- Outcome
- period of the cydese3
- Value
- about 20 mine3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“for single leaves of soybean (Glycine max L. Merr.) plants held at 30 °C”
e3“The period of the cydes was about 20 min”
Claim · model-written summary
Substomatal CO2 pressure stayed constant in most soybean leaves during the cycles and was above photosynthetic saturation
- Taxon
- soybeanGlycine maxe1
- Outcome
- substomatal carbon dioxide pressuree4
- Qualifier
- constant in the majority of leaves examinede4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“for single leaves of soybean (Glycine max L. Merr.) plants held at 30 °C”
e4“During these cycles the substomatal carbon dioxide pressure was constant in the majority of leaves examined, and was always above saturation for photosynthesis”
Claim · model-written summary
Most soybean stomata changed in aperture during the cycles, and very few were fully closed
- Taxon
- soybeanGlycine maxe1
- Organ / stage
- stomatae5
- Outcome
- changed in aperturee5
- Qualifier
- very few were ever fully closede5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“for single leaves of soybean (Glycine max L. Merr.) plants held at 30 °C”
e5“Epidermal impressions showed that most stomata changed in aperture during the cycles, and that very few were ever fully closed”
Claim · model-written summary
Water potential of soybean excised discs changed by at most 0.1 MPa between the minima and maxima of transpiration rate
- Taxon
- soybeanGlycine maxe1
- Outcome
- Water potentiale6
- Value
- 0·1 MPae6
- Qualifier
- from the minima to the maxima in transpiration ratee6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“for single leaves of soybean (Glycine max L. Merr.) plants held at 30 °C”
e6“Water potential measured on excised discs changed by at most 0·1 MPa from the minima to the maxima in transpiration rate”
Claim · model-written summary
In sunflower leaves grown at low PPFD, the increase in VPD decreased photosynthesis
- Taxon
- sunflower
Helianthus annuuse7 - Treatment
- the increase in VPDe7
- Outcome
- photosynthesise7
- Direction
- decreasede7
- Qualifier
- grown at low PPFDe7
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e7“for leaves of sunflower (Helianthus animus L.) grown at low PPFD, the increase in VPD led to leaf wilting and decreased photosynthesis”
Claim · model-written summary
In sunflower leaves grown at low PPFD, the increase in VPD caused leaf wilting
- Taxon
- sunflowerHelianthus annuuse7
- Treatment
- the increase in VPDe7
- Outcome
- leaf wiltinge7
- Qualifier
- grown at low PPFDe7
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e7“for leaves of sunflower (Helianthus animus L.) grown at low PPFD, the increase in VPD led to leaf wilting and decreased photosynthesis”
Claim · model-written summary
Sunflower turgor and photosynthesis recovered as stomatal conductance began to decrease
- Taxon
- sunflowerHelianthus annuuse7
- Outcome
- recovery of turgor and photosynthesise6
- Qualifier
- as stomatal conductance began to decreasee6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e7“for leaves of sunflower (Helianthus animus L.) grown at low PPFD, the increase in VPD led to leaf wilting and decreased photosynthesis”
e6“followed by recovery of turgor and photosynthesis as stomatal conductance began to decrease”
Claim · model-written summary
In sunflower, photosynthesis and conductance cycled approximately 180° out of phase
- Taxon
- sunflowerHelianthus annuuse7
- Outcome
- photosynthesis and conductancee6
- Value
- approximately 180°e6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e7“for leaves of sunflower (Helianthus animus L.) grown at low PPFD, the increase in VPD led to leaf wilting and decreased photosynthesis”
e6“In these leaves photosynthesis and conductance then cycled approximately 180° out of phase”
Claim · model-written summary
Decreased leaf conductance induced by high VPD is suggested to signal a decrease in soybean photosynthesis at CO2 saturation by a mechanism not related to mesophyll water deficit
- Taxon
- soybeansGlycine maxe0
- Outcome
- rate of photosynthesis at carbon dioxide saturatione0
- Qualifier
- a mechanism that was not related to a water deficit in the mesophylle0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“It is suggested that in soybeans decreased leaf conductance induced by high VPD provided a signal which decreased the rate of photosynthesis at carbon dioxide saturation by a mechanism that was not related to a water deficit in the mesophyll”